Appearance
â:In the classic "Doom" series, a particular level consists of a series of interconnected rooms and corridors. Suppose this level can be represented by a connected, undirected graph ( G ) with ( n ) vertices (rooms) and ( m ) edges (corridors). Each vertex ( v_i ) has a weight ( w_i ), representing the difficulty of the room, and each edge ( e_{ij} ) has a weight ( c_{ij} ), representing the time to traverse the corridor between room ( v_i ) and room ( v_j ).Sub-problem 1:Given the graph ( G ), find the minimum spanning tree (MST) of ( G ). Let the total weight of this MST be ( T ). Write down the expression for ( T ) in terms of ( w_i ) and ( c_{ij} ).Sub-problem 2:Assume you are an illustrator tasked with designing a mural for each room. You have a limited time ( H ) to complete the murals. The time ( t_i ) to design a mural in room ( v_i ) is proportional to the weight ( w_i ) of the room, given by ( t_i = k cdot w_i ), where ( k ) is a constant. Find the maximum number of rooms you can complete murals for within the time ( H ).
đ§ :<think>Alright, so I have this problem about the "Doom" series level represented as a graph. It's split into two sub-problems. Let me try to tackle them one by one.Starting with Sub-problem 1: I need to find the minimum spanning tree (MST) of the graph G. The total weight of this MST is T, and I have to express T in terms of the weights w_i of the vertices and the weights c_ij of the edges.Hmm, okay. I remember that a minimum spanning tree connects all the vertices of a graph with the minimum possible total edge weight. So, in this case, since the graph is connected and undirected, Krusky's or Prim's algorithm could be used to find the MST. But the question isn't asking for the algorithm; it's asking for an expression for T.Wait, but the vertices have weights too. Does that affect the MST? I think in the standard MST problem, only the edges have weights. The vertices don't directly contribute to the total weight of the MST. So, maybe the vertex weights w_i aren't directly part of the MST's total weight T. Instead, T is just the sum of the edge weights in the MST.So, if that's the case, then T would be the sum of c_ij for all edges in the MST. Let me write that down:T = ÎŖ c_ij for all edges e_ij in the MST.But the problem mentions both w_i and c_ij. Maybe I'm missing something. Is there a possibility that the vertex weights are somehow incorporated into the edge weights? Or perhaps the problem is considering some kind of weighted MST where both vertices and edges have weights? I don't recall such a standard problem.Wait, let me think again. The problem says each vertex v_i has a weight w_i, representing the difficulty of the room, and each edge e_ij has a weight c_ij, representing the time to traverse the corridor. So, when constructing the MST, we are only concerned with the edges, right? Because the MST is about connecting all the rooms with the minimum traversal time. The difficulty of the rooms (vertex weights) doesn't directly affect the traversal time between them.Therefore, I think the total weight T is just the sum of the edge weights in the MST. So, the expression for T is the sum of c_ij for all edges in the MST.Moving on to Sub-problem 2: I'm an illustrator with limited time H to complete murals. The time t_i to design a mural in room v_i is proportional to w_i, given by t_i = k * w_i. I need to find the maximum number of rooms I can complete murals for within time H.Okay, so this seems like a scheduling problem where I have to select as many rooms as possible such that the total time doesn't exceed H. Since t_i = k * w_i, the total time for selecting a set of rooms S is ÎŖ (k * w_i) for all i in S. I need to maximize |S| such that ÎŖ (k * w_i) ⤠H.Since k is a constant, I can factor it out: k * ÎŖ w_i ⤠H. Therefore, ÎŖ w_i ⤠H / k.So, the problem reduces to selecting the maximum number of rooms such that the sum of their weights w_i is at most H / k. To maximize the number of rooms, I should select the rooms with the smallest w_i first because that way, I can fit more rooms within the total weight limit.So, the approach is:1. Sort all the rooms in ascending order of their weights w_i.2. Start adding the rooms from the smallest w_i until adding another room would exceed H / k.3. The number of rooms added before exceeding the limit is the maximum number of rooms I can complete.Therefore, the maximum number of rooms is the largest integer m such that the sum of the m smallest w_i is ⤠H / k.Let me denote the sorted weights as w_{(1)} ⤠w_{(2)} ⤠... ⤠w_{(n)}. Then, the maximum m is the largest m where ÎŖ_{i=1}^m w_{(i)} ⤠H / k.So, the answer is the maximum m satisfying that inequality.Wait, but the problem doesn't specify whether the rooms are independent or if there's any constraint based on the graph structure. It just says I'm designing murals for each room, so I think it's just a matter of selecting rooms without considering their connections. So, the graph structure doesn't affect this part; it's purely a knapsack-like problem where I want to maximize the number of items (rooms) with the smallest weights (difficulties) without exceeding the total weight capacity (H / k).Therefore, my conclusion is that for Sub-problem 1, T is the sum of the edge weights in the MST, and for Sub-problem 2, the maximum number of rooms is determined by selecting the rooms with the smallest w_i until the total time is within H.Final AnswerSub-problem 1: The total weight ( T ) of the MST is the sum of the edge weights in the MST. Thus, ( T = sum c_{ij} ) for all edges ( e_{ij} ) in the MST.Sub-problem 2: The maximum number of rooms is the largest integer ( m ) such that the sum of the ( m ) smallest weights ( w_i ) is at most ( frac{H}{k} ).Final Answers:1. ( boxed{T = sum c_{ij}} ) for all edges in the MST.2. The maximum number of rooms is ( boxed{m} ) where ( m ) is the largest integer satisfying ( sum_{i=1}^{m} w_{(i)} leq frac{H}{k} ).However, since the problem asks for expressions, perhaps the second answer should be presented as the maximum m. But since it's a box, maybe just stating the expression.Wait, actually, for the first sub-problem, the answer is simply the sum of the edge weights in the MST. So, in terms of c_ij, it's the sum over all edges in the MST. So, the expression is T equals the sum of c_ij for edges in the MST.For the second sub-problem, the maximum number of rooms is the maximum m such that the sum of the m smallest w_i is less than or equal to H/k. So, the expression is the maximum m where ÎŖ_{i=1}^m w_{(i)} ⤠H/k.But since the problem asks to write down the expression, perhaps for the first part, it's just T = sum of c_ij in MST, and for the second, it's the maximum m such that sum of m smallest w_i ⤠H/k.But in the final answer, I need to put them in boxes.So, for Sub-problem 1, the expression is the sum of the edge weights in the MST, which is T = ÎŖ c_ij for edges in MST.For Sub-problem 2, the maximum number of rooms is the maximum m where the sum of the m smallest w_i ⤠H/k.But how to write that in a box? Maybe as:1. ( boxed{T = sum c_{ij}} ) where the sum is over all edges in the MST.2. ( boxed{max left{ m mid sum_{i=1}^{m} w_{(i)} leq frac{H}{k} right}} )But perhaps the second answer is better written as the maximum m such that the sum of the m smallest w_i is ⤠H/k.Alternatively, since the problem says "find the maximum number of rooms", it's an integer, so perhaps we can denote it as m_max, but since it's an expression, maybe it's better to write it as the maximum m.But I think the way I wrote it is acceptable.So, final answers:1. ( boxed{T = sum c_{ij}} ) for all edges in the MST.2. ( boxed{max left{ m mid sum_{i=1}^{m} w_{(i)} leq frac{H}{k} right}} )But wait, in the first problem, the question says "write down the expression for T in terms of w_i and c_ij". So, perhaps I need to include both? But in the MST, the vertex weights don't contribute. So, T is only the sum of c_ij.So, the first answer is correct as T is the sum of c_ij in the MST.The second answer is the maximum m such that the sum of the m smallest w_i is ⤠H/k.So, I think that's it.</think>
â:Consider a reluctant mediator who is tasked with finding a peaceful resolution to an international conflict involving three countries: A, B, and C. The mediator must allocate resources to each country in such a way that the total allocation maximizes the chances of peace. The mediator models the peace probability (P) as a function of the resources (x_A), (x_B), and (x_C) allocated to countries A, B, and C respectively. The function is given by:[ P(x_A, x_B, x_C) = frac{exp(k_1 x_A + k_2 x_B + k_3 x_C)}{1 + exp(k_1 x_A + k_2 x_B + k_3 x_C)} ]where (k_1, k_2), and (k_3) are constants representing the sensitivity of each country's peace probability to the resources allocated.Sub-problems:1. Given that the total resources available (R) is constrained by (x_A + x_B + x_C = R), derive the optimal allocation (x_A^*), (x_B^*), and (x_C^*) that maximizes the peace probability (P(x_A, x_B, x_C)).2. Suppose that the mediator is required to ensure that the allocated resources to any country do not fall below a certain minimum threshold (T), i.e., (x_A, x_B, x_C geq T). Reformulate the optimization problem and determine if the constraint (x_A + x_B + x_C = R) along with (x_A, x_B, x_C geq T) allows for a feasible solution. If so, discuss the conditions under which such a solution exists.
đ§ :<think>Alright, so I have this problem where a mediator is trying to allocate resources to three countries, A, B, and C, to maximize the probability of peace. The peace probability is given by this logistic function:[ P(x_A, x_B, x_C) = frac{exp(k_1 x_A + k_2 x_B + k_3 x_C)}{1 + exp(k_1 x_A + k_2 x_B + k_3 x_C)} ]And the total resources allocated must add up to R:[ x_A + x_B + x_C = R ]First, I need to figure out the optimal allocation (x_A^*), (x_B^*), and (x_C^*) that maximizes P. Then, in the second part, I have to consider a minimum threshold T for each country's allocation and see if a feasible solution exists under that constraint.Starting with the first sub-problem. Since the mediator wants to maximize P, which is a function of the resources allocated, I should think about how to maximize this function given the constraint on the total resources.Looking at the function P, it's a logistic function, which is S-shaped. It increases as the exponent increases. So, to maximize P, we need to maximize the exponent (k_1 x_A + k_2 x_B + k_3 x_C). Because the logistic function is monotonically increasing, maximizing the exponent will maximize P.Therefore, the problem reduces to maximizing (k_1 x_A + k_2 x_B + k_3 x_C) subject to (x_A + x_B + x_C = R).This is a linear optimization problem. The objective function is linear, and the constraint is also linear. So, the maximum occurs at the vertices of the feasible region.In linear optimization, the maximum of a linear function over a convex set (like the simplex defined by (x_A + x_B + x_C = R) and (x_A, x_B, x_C geq 0)) occurs at an extreme point, which in this case would be when as much as possible is allocated to the variable with the highest coefficient.So, if (k_1), (k_2), and (k_3) are all positive, the optimal allocation would be to allocate all resources to the country with the highest sensitivity. For example, if (k_1 > k_2) and (k_1 > k_3), then (x_A^* = R), and (x_B^* = x_C^* = 0).Wait, but is that necessarily true? Let me think. Since the function to maximize is linear, yes, the maximum is achieved by putting as much as possible into the variable with the highest coefficient. So, if (k_1) is the largest, then all resources go to A.But what if some of the (k)s are negative? Hmm, the problem statement says (k_1, k_2, k_3) are constants representing sensitivity. It doesn't specify if they are positive or negative. If a (k) is negative, then increasing (x) for that country would decrease the exponent, which would decrease P. So, in that case, we would want to allocate as little as possible to that country.But in the first sub-problem, there are no lower bounds on (x_A, x_B, x_C), only the total sum is R. So, if a country has a negative sensitivity, we would allocate zero to it, and allocate the rest to the country with the highest positive sensitivity.So, to formalize this, we can say that the optimal allocation is to allocate all resources to the country with the highest (k_i), and zero to the others, provided that (k_i) is positive. If all (k_i) are negative, then allocating zero to all would maximize the exponent, but since the total must be R, we have to allocate all to the least negative one, which would minimize the decrease in the exponent.Wait, actually, if all (k_i) are negative, then the exponent is negative, and increasing the exponent (making it less negative) would increase P. So, to maximize the exponent, we should allocate as much as possible to the country with the least negative (k_i), i.e., the one closest to zero.Therefore, in general, the optimal allocation is to allocate all resources to the country with the highest (k_i), regardless of the sign, because if (k_i) is positive, you want to maximize it; if all are negative, you want to minimize the negative impact, so allocate to the least negative.But wait, if all (k_i) are negative, then the exponent is negative, and the logistic function is increasing, so a higher exponent (closer to zero) gives a higher P. So, yes, allocate all to the country with the highest (k_i), which in this case is the least negative.So, in summary, the optimal allocation is to put all resources into the country with the highest (k_i), and zero into the others.But let me verify this with calculus. Maybe using Lagrange multipliers.Let me set up the Lagrangian:[ mathcal{L} = k_1 x_A + k_2 x_B + k_3 x_C - lambda (x_A + x_B + x_C - R) ]Taking partial derivatives:[ frac{partial mathcal{L}}{partial x_A} = k_1 - lambda = 0 ][ frac{partial mathcal{L}}{partial x_B} = k_2 - lambda = 0 ][ frac{partial mathcal{L}}{partial x_C} = k_3 - lambda = 0 ][ frac{partial mathcal{L}}{partial lambda} = -(x_A + x_B + x_C - R) = 0 ]From the first three equations, we get:[ k_1 = lambda ][ k_2 = lambda ][ k_3 = lambda ]Which implies (k_1 = k_2 = k_3). But unless all (k_i) are equal, this can't be satisfied. Therefore, the maximum occurs at the boundary of the feasible region.So, when the (k_i) are not all equal, the maximum occurs at a corner point where two variables are zero, and the third is R. Therefore, confirming that the optimal allocation is to allocate all resources to the country with the highest (k_i).So, for the first sub-problem, the optimal allocation is:- If (k_1 geq k_2) and (k_1 geq k_3), then (x_A^* = R), (x_B^* = 0), (x_C^* = 0).- Similarly for the other countries if their (k) is the highest.Now, moving on to the second sub-problem. Here, each country must have at least a minimum threshold T. So, (x_A geq T), (x_B geq T), (x_C geq T), and (x_A + x_B + x_C = R).First, we need to check if a feasible solution exists. That is, can we allocate at least T to each country without exceeding R?The total minimum required is (3T). So, if (3T leq R), then it's feasible. Otherwise, it's not.So, the condition for feasibility is (R geq 3T).Assuming (R geq 3T), we can proceed to find the optimal allocation.Now, the problem is to maximize (k_1 x_A + k_2 x_B + k_3 x_C) subject to:[ x_A + x_B + x_C = R ][ x_A geq T ][ x_B geq T ][ x_C geq T ]This is again a linear optimization problem with inequality constraints.To solve this, we can use the method of considering the constraints and seeing how they affect the allocation.Since we have to allocate at least T to each country, the remaining resources after allocating T to each is (R - 3T). Let's denote this remaining amount as (S = R - 3T).Now, we need to allocate this remaining S to the countries in a way that maximizes the exponent (k_1 x_A + k_2 x_B + k_3 x_C).Given that, we should allocate the remaining S to the country with the highest (k_i), because each additional unit allocated to that country gives the highest increase in the exponent.Therefore, the optimal allocation would be:- Allocate T to each country.- Then, allocate the remaining S = R - 3T to the country with the highest (k_i).So, if (k_1) is the highest, then:[ x_A^* = T + S = T + (R - 3T) = R - 2T ][ x_B^* = T ][ x_C^* = T ]Similarly, if (k_2) is the highest, then:[ x_B^* = R - 2T ][ x_A^* = T ][ x_C^* = T ]And the same for (k_3).But wait, what if two countries have the same highest (k_i)? For example, if (k_1 = k_2 > k_3). Then, we can allocate the remaining S to both A and B equally, or proportionally, but since the objective is linear, any allocation that maximizes the sum would be acceptable. However, in linear optimization, if two variables have the same coefficient, you can distribute the remaining resources between them in any way, and the objective function will be the same. So, in that case, the allocation could be (x_A = T + S/2), (x_B = T + S/2), (x_C = T), or any other combination that sums to S between A and B.But in the absence of specific instructions, we can assume that we allocate all remaining S to the country with the highest (k_i), even if there are ties, because the problem doesn't specify how to handle ties. Alternatively, if there are ties, the allocation could be split, but the maximum would still be achieved.Wait, actually, in linear optimization, if two variables have the same coefficient, the optimal solution can be anywhere along the edge connecting the two corner points. So, in that case, the allocation could be split between the tied countries.But for simplicity, unless specified otherwise, we can assume that we allocate all remaining S to the country with the highest (k_i), even if there are ties, but in reality, the optimal solution is not unique in that case.But perhaps the problem expects us to consider that if multiple countries have the same highest (k_i), we can allocate the remaining S to any of them, or split it.But in any case, the key point is that after allocating T to each, the remaining S is allocated to the country with the highest (k_i).Therefore, the optimal allocation is:- Allocate T to each country.- Allocate the remaining (R - 3T) to the country with the highest (k_i).So, summarizing:If (R geq 3T), then the optimal allocation is:- (x_j^* = T + (R - 3T)) for the country j with the highest (k_j)- (x_i^* = T) for the other countries i â jIf (R < 3T), then no feasible solution exists because we cannot allocate T to each country without exceeding R.Therefore, the conditions for feasibility are (R geq 3T).To confirm this, let's consider an example. Suppose R = 10, T = 2, and (k_1 = 3), (k_2 = 2), (k_3 = 1). Then, 3T = 6 ⤠10, so feasible. Allocate 2 to each, then 10 - 6 = 4 to A. So, x_A = 6, x_B = 2, x_C = 2.If R = 5, T = 2, then 3T = 6 > 5, so not feasible.Another example: R = 9, T = 3. 3T = 9, so exactly feasible. Allocate 3 to each, no remaining resources. So, x_A = x_B = x_C = 3.If (k_1 = k_2 = 4), (k_3 = 2), R = 10, T = 2. Then, allocate 2 to each, remaining 4. Since k1 and k2 are equal, we can allocate 4 to either A or B, or split it. But the maximum is achieved either way.So, yes, this approach seems correct.Therefore, the answers are:1. The optimal allocation is to allocate all resources to the country with the highest (k_i), i.e., if (k_1 geq k_2) and (k_1 geq k_3), then (x_A^* = R), (x_B^* = 0), (x_C^* = 0), and similarly for the other countries.2. The problem is feasible if and only if (R geq 3T). If this condition is satisfied, the optimal allocation is to allocate T to each country and then allocate the remaining (R - 3T) to the country with the highest (k_i). If there are ties in the highest (k_i), the remaining resources can be allocated to any of the tied countries or split among them.</think>
â:A daughter studying botany at the university level, with a keen interest in plant genetics, is conducting research on the inheritance patterns of two specific genes in a certain plant species. Gene A and Gene B are located on different chromosomes and thus assort independently. Gene A has two alleles: A (dominant) and a (recessive), while Gene B has two alleles: B (dominant) and b (recessive). She crosses two plants that are both heterozygous for both genes (AaBb x AaBb).1. Using a Punnett square, determine the probability that an offspring plant will exhibit the dominant phenotype for both genes (A-B-).2. Assuming the population of offspring plants follows a binomial distribution with n = 1000 (total number of offspring plants), calculate the expected number of offspring that will exhibit the dominant phenotype for both genes.
đ§ :<think>Okay, so I have this problem about plant genetics, and I need to figure out the probability that an offspring plant will exhibit the dominant phenotype for both genes, and then use that to find the expected number in a population of 1000 plants. Hmm, let me start by understanding what's given.First, the daughter is studying two genes, Gene A and Gene B, which are on different chromosomes. That means they assort independently, right? So, the inheritance of one doesn't affect the other. Both genes have two alleles each: A and a for Gene A, and B and b for Gene B. The parents are both heterozygous for both genes, so their genotype is AaBb. She's crossing them, so it's an AaBb x AaBb cross.Alright, for the first part, I need to determine the probability that an offspring will exhibit the dominant phenotype for both genes. Since both genes are independently assorting, I can probably tackle each gene separately and then combine the probabilities.Starting with Gene A. Each parent is Aa, so when they cross, the possible gametes are A and a. The Punnett square for Gene A would look like this:``` A aA AA Aaa Aa aa```So, the possible genotypes are AA, Aa, Aa, and aa. The phenotypes would be dominant (AA and Aa) and recessive (aa). The probability of dominant phenotype for Gene A is the probability of AA or Aa. There are 4 possible outcomes, 3 of which result in dominant phenotype. Wait, actually, no. Let me think again.Wait, the Punnett square for Gene A has four boxes: AA, Aa, Aa, aa. So, three out of four have at least one dominant allele, so the probability of dominant phenotype is 3/4. Similarly, for Gene B, it's the same situation because it's also Aa x Aa. So, the probability of dominant phenotype for Gene B is also 3/4.Since the genes are independent, the probability that both occur together is the product of their individual probabilities. So, the probability for both dominant phenotypes is (3/4) * (3/4) = 9/16. Let me verify that.Alternatively, I can construct a dihybrid cross Punnett square. Since both genes are independently assorting, the combined Punnett square would have 16 possible outcomes. Let me sketch it out mentally.Each parent can produce four types of gametes: AB, Ab, aB, ab. So, the Punnett square would be:``` AB Ab aB abAB AABB AABb AaBB AaBbAb AABb AAbb AaBb AabbaB AaBB AaBb aaBB aaBbab AaBb Aabb aaBb aabb```Wait, actually, each parent is AaBb, so each gamete has one allele for each gene. So, the gametes are AB, Ab, aB, ab, each with equal probability of 25%. So, the Punnett square would be 4x4, resulting in 16 possible combinations.Looking at the phenotypes, dominant for both would require at least one dominant allele for each gene. So, any genotype that isn't aa for Gene A or bb for Gene B. So, let's count how many of the 16 have at least one A and at least one B.Looking at the Punnett square:- The first row (AB gamete) gives AABB, AABb, AaBB, AaBb. All of these have at least one A and one B, so dominant phenotype.- The second row (Ab gamete) gives AABb, AAbb, AaBb, Aabb. Here, AAbb and Aabb have bb, so recessive for Gene B. So, two out of four in this row have dominant phenotype.- The third row (aB gamete) gives AaBB, AaBb, aaBB, aaBb. Here, aaBB and aaBb have aa, so recessive for Gene A. So, two out of four in this row have dominant phenotype.- The fourth row (ab gamete) gives AaBb, Aabb, aaBb, aabb. All of these have either aa or bb, so all four have at least one recessive phenotype. So, none have dominant for both.Wait, no. Let me correct that. In the fourth row, the genotypes are AaBb, Aabb, aaBb, aabb. So, AaBb has both dominant, Aabb has dominant A but recessive B, aaBb has recessive A but dominant B, and aabb has both recessive. So, only AaBb in this row has both dominant phenotypes. So, actually, one out of four in the fourth row.Wait, hold on, maybe I should count each cell individually.Looking at all 16 cells:1. AABB - dominant both2. AABb - dominant both3. AaBB - dominant both4. AaBb - dominant both5. AABb - dominant both6. AAbb - dominant A, recessive B7. AaBb - dominant both8. Aabb - dominant A, recessive B9. AaBB - dominant both10. AaBb - dominant both11. aaBB - recessive A, dominant B12. aaBb - recessive A, dominant B13. AaBb - dominant both14. Aabb - dominant A, recessive B15. aaBb - recessive A, dominant B16. aabb - recessive bothNow, let's count how many have dominant both. So, looking through each:1. Yes2. Yes3. Yes4. Yes5. Yes6. No7. Yes8. No9. Yes10. Yes11. No12. No13. Yes14. No15. No16. NoSo, counting the Yeses: 1,2,3,4,5,7,9,10,13. That's 9 out of 16. So, 9/16. That matches the earlier calculation of (3/4)*(3/4) = 9/16. So, that seems correct.Therefore, the probability that an offspring exhibits dominant phenotype for both genes is 9/16.Now, moving on to the second part. Assuming the population follows a binomial distribution with n = 1000, calculate the expected number of offspring that exhibit the dominant phenotype for both genes.In a binomial distribution, the expected value (mean) is given by n*p, where p is the probability of success. Here, success is an offspring exhibiting dominant phenotype for both genes, which we found to be 9/16.So, expected number = 1000 * (9/16). Let me compute that.First, 9 divided by 16 is equal to 0.5625. Then, 1000 multiplied by 0.5625 is 562.5.So, the expected number is 562.5.Wait, but since we can't have half a plant, in reality, we'd expect around 562 or 563 plants. But since the question asks for the expected number, it's okay to have a fractional value because expectation can be a non-integer.So, summarizing:1. The probability is 9/16.2. The expected number is 562.5.I think that's it. Let me just make sure I didn't make any mistakes in the Punnett square counting. I had 9 out of 16 with dominant both, which seems right because each gene has a 3/4 chance, and 3/4 * 3/4 is 9/16. So, yes, that seems correct.And for the binomial expectation, n*p is straightforward. So, 1000 * 9/16 is indeed 562.5. So, I think I'm confident in these answers.Final Answer1. The probability is boxed{dfrac{9}{16}}.2. The expected number is boxed{562.5}.</think>
â:A Gaelic literature author is using an online platform to promote endangered Celtic languages. The author has noticed that the number of followers on the platform increases exponentially each month, and the total number of pieces of literature (both prose and poetry) published grows according to a Fibonacci sequence.1. The number of followers (F(t)) on the platform after (t) months is modeled by the function (F(t) = F_0 cdot e^{kt}), where (F_0) is the initial number of followers and (k) is a constant growth rate. Given that the author had 500 followers initially and gained 1500 followers after 3 months, find the exact value of the growth rate (k).2. The number of pieces of literature published after (n) months follows the Fibonacci sequence (L(n)), where (L(n) = L(n-1) + L(n-2)) with initial conditions (L(0) = 1) and (L(1) = 1). If the author plans to publish a special anthology once the total number of published pieces exceeds 1000, determine the smallest value of (n) for which (L(n) > 1000).
đ§ :<think>Okay, so I have two problems here about a Gaelic literature author promoting endangered Celtic languages. The first one is about exponential growth of followers, and the second one is about the Fibonacci sequence for the number of published pieces. Let me tackle them one by one.Starting with problem 1: The number of followers F(t) after t months is modeled by F(t) = F0 * e^(kt). They gave me that F0 is 500, and after 3 months, the followers increased to 1500. I need to find the exact value of k.Alright, so let's plug in the values. At t=0, F(0) = 500, which makes sense because that's the initial number. After 3 months, t=3, F(3) = 1500. So, substituting into the formula:1500 = 500 * e^(3k)I can divide both sides by 500 to simplify:1500 / 500 = e^(3k)3 = e^(3k)Now, to solve for k, I need to take the natural logarithm of both sides. Remember, ln(e^x) = x.ln(3) = ln(e^(3k))ln(3) = 3kSo, k = ln(3) / 3Hmm, that seems straightforward. Let me double-check. If I plug k back into the equation:F(t) = 500 * e^( (ln(3)/3) * t )At t=3, that becomes:500 * e^( (ln(3)/3)*3 ) = 500 * e^(ln(3)) = 500 * 3 = 1500Yep, that works. So k is ln(3)/3.Moving on to problem 2: The number of pieces of literature L(n) follows a Fibonacci sequence. The recurrence relation is L(n) = L(n-1) + L(n-2), with L(0) = 1 and L(1) = 1. The author wants to publish a special anthology once the total exceeds 1000. I need to find the smallest n where L(n) > 1000.Alright, Fibonacci sequence starting with L(0)=1 and L(1)=1. Let me write out the terms until I exceed 1000.Let me list them step by step:n : L(n)0 : 11 : 12 : L(1) + L(0) = 1 + 1 = 23 : L(2) + L(1) = 2 + 1 = 34 : L(3) + L(2) = 3 + 2 = 55 : 5 + 3 = 86 : 8 + 5 = 137 : 13 + 8 = 218 : 21 + 13 = 349 : 34 + 21 = 5510 : 55 + 34 = 8911 : 89 + 55 = 14412 : 144 + 89 = 23313 : 233 + 144 = 37714 : 377 + 233 = 61015 : 610 + 377 = 98716 : 987 + 610 = 1597Wait, so at n=15, L(15)=987, which is just below 1000. Then at n=16, it's 1597, which is above 1000. So the smallest n where L(n) > 1000 is 16.But let me make sure I didn't skip any steps or make a calculation error. Let me recount:Starting from n=0:0:11:12:23:34:55:86:137:218:349:5510:8911:14412:23313:37714:61015:98716:1597Yep, that seems correct. So n=16 is the first term exceeding 1000.Alternatively, I could use the closed-form formula for Fibonacci numbers, Binet's formula, which is:L(n) = (phi^n - psi^n) / sqrt(5)Where phi is the golden ratio (1 + sqrt(5))/2 â 1.618, and psi is (1 - sqrt(5))/2 â -0.618.Since |psi| < 1, psi^n becomes negligible for large n, so L(n) â phi^n / sqrt(5). So to find n where L(n) > 1000, we can approximate:phi^n / sqrt(5) > 1000phi^n > 1000 * sqrt(5)Take natural logs:n * ln(phi) > ln(1000 * sqrt(5))n > ln(1000 * sqrt(5)) / ln(phi)Compute ln(1000 * sqrt(5)):ln(1000) + ln(sqrt(5)) = ln(10^3) + (1/2) ln(5) = 3 ln(10) + (1/2) ln(5)Compute ln(10) â 2.302585, ln(5) â 1.60944So 3*2.302585 â 6.907755(1/2)*1.60944 â 0.80472Total â 6.907755 + 0.80472 â 7.712475ln(phi) â ln(1.618034) â 0.481212So n > 7.712475 / 0.481212 â 16.02So n must be at least 17? Wait, but earlier when I listed out the Fibonacci numbers, n=16 gives 1597, which is over 1000. So why does this approximation give nâ16.02? Hmm.Wait, maybe because the approximation neglects the psi^n term, which for n=16 is (-0.618)^16, which is positive and about 0.000015, so negligible, but still, the exact value is 1597, which is already over 1000. So perhaps the approximation is slightly off because it's using the limit as n approaches infinity, but for finite n, the exact value is a bit higher.Wait, but according to the exact calculation, n=16 is the first term over 1000. So maybe the approximation is giving nâ16.02, which is just over 16, so the next integer is 17, but actually, since n=16 is already over, we don't need to go to 17.So perhaps the approximation is slightly underestimating because it's neglecting the psi^n term, which is positive here (since n is even, psi^n is positive). So actually, L(n) is slightly larger than phi^n / sqrt(5). So maybe the exact value is a bit larger, so n=16 is sufficient.Alternatively, perhaps I should compute it more accurately.Compute L(n) using Binet's formula for n=16:phi^16 / sqrt(5) - psi^16 / sqrt(5)Compute phi^16:phi â 1.618034phi^2 â 2.618034phi^4 â (2.618034)^2 â 6.854phi^8 â (6.854)^2 â 46.97phi^16 â (46.97)^2 â 2206.3Similarly, psi^16:psi â -0.618034psi^2 â 0.618034^2 â 0.381966psi^4 â (0.381966)^2 â 0.145898psi^8 â (0.145898)^2 â 0.021287psi^16 â (0.021287)^2 â 0.000453So L(16) â (2206.3 - 0.000453)/2.23607 â (2206.2995)/2.23607 â 986. So wait, that's about 986, but earlier when I calculated the Fibonacci numbers, L(16) was 1597. That's a discrepancy.Wait, no, that can't be. Wait, maybe I messed up the powers.Wait, phi^16 is actually (phi^8)^2. Let me compute phi^1 more carefully.phi^1 â 1.618034phi^2 â 2.618034phi^3 â phi^2 * phi â 2.618034 * 1.618034 â 4.236068phi^4 â phi^3 * phi â 4.236068 * 1.618034 â 6.854phi^5 â 6.854 * 1.618034 â 11.090phi^6 â 11.090 * 1.618034 â 17.944phi^7 â 17.944 * 1.618034 â 29.034phi^8 â 29.034 * 1.618034 â 46.97phi^9 â 46.97 * 1.618034 â 76.01phi^10 â 76.01 * 1.618034 â 122.99phi^11 â 122.99 * 1.618034 â 198.99phi^12 â 198.99 * 1.618034 â 322.0phi^13 â 322.0 * 1.618034 â 520.0phi^14 â 520.0 * 1.618034 â 841.0phi^15 â 841.0 * 1.618034 â 1360.0phi^16 â 1360.0 * 1.618034 â 2200.0Similarly, psi^16 is (psi^8)^2. Let's compute psi^8:psi â -0.618034psi^2 â 0.618034^2 â 0.381966psi^4 â (0.381966)^2 â 0.145898psi^8 â (0.145898)^2 â 0.021287psi^16 â (0.021287)^2 â 0.000453So, L(16) = (phi^16 - psi^16)/sqrt(5) â (2200 - 0.000453)/2.23607 â 2200 / 2.23607 â 984. So that's about 984, but when I computed the Fibonacci numbers earlier, L(16) was 1597. That's a big difference. So I must have messed up.Wait, no, actually, in the Fibonacci sequence, L(n) is the nth term, but in Binet's formula, it's the nth Fibonacci number. But in our case, L(n) is defined as L(0)=1, L(1)=1, L(2)=2, etc. So actually, the standard Fibonacci sequence is F(0)=0, F(1)=1, F(2)=1, F(3)=2, etc. So our L(n) is shifted.Wait, let me check:Standard Fibonacci:F(0)=0F(1)=1F(2)=1F(3)=2F(4)=3F(5)=5F(6)=8F(7)=13F(8)=21F(9)=34F(10)=55F(11)=89F(12)=144F(13)=233F(14)=377F(15)=610F(16)=987F(17)=1597Wait, so in our problem, L(n) is defined as L(0)=1, L(1)=1, L(2)=2, L(3)=3, L(4)=5, etc. So that's actually the standard Fibonacci sequence shifted by one. So L(n) = F(n+1), where F(n) is the standard Fibonacci sequence with F(0)=0.Therefore, L(n) = F(n+1). So if we want L(n) > 1000, that corresponds to F(n+1) > 1000.From the standard Fibonacci sequence, F(17)=1597, which is the first Fibonacci number over 1000. Therefore, L(n) = F(n+1) > 1000 when n+1=17, so n=16.So that matches our earlier calculation. So n=16 is the smallest n where L(n) > 1000.Therefore, the answer is n=16.But just to make sure, let me list out L(n) again:n : L(n)0 :11 :12 :23 :34 :55 :86 :137 :218 :349 :5510 :8911 :14412 :23313 :37714 :61015 :98716 :1597Yes, so at n=16, L(n)=1597 > 1000, and n=15 is 987 < 1000. So n=16 is the smallest n.So, summarizing:Problem 1: k = ln(3)/3Problem 2: n=16Final Answer1. The growth rate ( k ) is boxed{dfrac{ln 3}{3}}.2. The smallest value of ( n ) is boxed{16}.</think>