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question:How can we calculate the probability of distributing indistinguishable balls into distinguishable bins such that each bin contains at least one ball, while avoiding the pitfall of assuming equal likelihood for each distribution?
answer:To calculate the probability without assuming equal likelihood, we can use the same case method as before: Case 1: One bin has 4 balls, and the others have 1 each. The number of ways this can happen is 7. Case 2: One bin has 3 balls, another has 2, and the others have 1 each. The number of ways this can happen is (7 choose 2) * 2 = 42. Case 3: Three bins have 2 balls each, and the others have 1 each. The number of ways this can happen is (7 choose 3) = 35. The total number of ways to distribute 10 indistinguishable balls into 7 distinguishable bins is 7^10. Therefore, the probability of having at least one ball in each bin is (7 + 42 + 35) / 7^10.
question:In a group of physics graduates from a university, 30% started with a salary of 30,000 or more. If five graduates are chosen randomly, what is the probability that all five received a starting salary of at least 30,000?
answer:The probability that all five randomly selected graduates had a starting salary of 30,000 or more is 0.243%. This probability can be calculated as follows: {eq}begin{align*} &= (text{Probability for each graduate})^{text{Number of graduates selected}} &= (30%)^5 &= (0.30)^5 &= 0.00243 &= 0.243% end{align*} {/eq}
question:Factor the following quadratic: -4x^2 + 24x + 988
answer:First, we can factor out a -4 from the expression: -4x^2 + 24x + 988 = -4(x^2 - 6x - 247) Next, we can factor the quadratic inside the parentheses: -4(x^2 - 6x - 247) = -4(x-19)(x+13) Therefore, the factors of -4x^2 + 24x + 988 are -4(x-19)(x+13). The answer is -4(x-19)(x+13)
question:What is the characteristic polynomial of the matrix given below? left( begin{array}{ccc} -10 & 7 & -7 8 & 8 & -2 2 & 6 & 7 end{array} right)
answer:To find the characteristic polynomial, we use the determinant of the matrix with the identity matrix augmented to it and replace one of the diagonal elements with -x. The characteristic polynomial p(x) is given by the determinant: p(x) = det left( begin{array}{ccc|c} -10-x & 7 & -7 & 0 8 & 8 & -2 & 0 2 & 6 & 7 & 0 end{array} right) After expanding the determinant, we get: p(x) = (-10-x)((8)(7) - (-2)(6)) - (7)((8)(7) - (-2)(2)) + (-7)((8)(6) - (2)(8)) p(x) = (-10-x)(56 + 12) - (7)(56 - 4) + (-7)(48 - 16) p(x) = (-10-x)(68) - (7)(52) + (-7)(32) p(x) = -680 - 68x - 364 + 224 + 224 p(x) = -680 - 68x p(x) = -68x - 680 p(x) = x^3 - 5x^2 - 124x + 1324 However, there seems to be a typo in the original answer. The correct characteristic polynomial is: p(x) = x^3 - 5x^2 - 124x + 1324