中原大學九十學年度碩士班入學招生考試

4月28日  第2節   電子系丙組 誠實是我們珍視的美德,
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科目:工程數學 (共2頁 第1頁)

1. Let P be any solution of AX=B, and Q is a solution of AX=0.
(a) What is the form of every solution of AX=B. (3%)
(b) Please prove it. (7%)

2. Letand AX=B.
(a) Find the inverse of A (that is A-1). (7%)
(b) Solve for the solution of X. (3%)

3. Consider the system:
(a) Find the eigenvalues and eigenvectors of A. (10%)
(b) Solve the solutions for x1, x2, and x3. (10%)

4. Ifis the coordinate vector with respect to [e1, e2].
(a) Please find the transition matrix from [a1, a2] to [e1, e2]. (5%)
(b) Please find the coordinates of x with respect to [a1, a2]. (5%)

5. Suppose the number of earthquakes that occur in T weeks in Taiwan is a Poisson random variable, N, with expected value λT. Find the probability that at least 3 earthquakes occur during the next 2 weeks. (10%)

6. Let X and Y be positive independent random variables with the identical probability density function ae-x for x > 0 and ae-y for y > 0, respectively, where a is a constant. Find the constant a and the joint probability density function of U= X/Y and V= X+Y. (20%)

7. Show the following two fundamental inequalities in probability theory.
(a) If X is a random variable that takes only nonnegative values, then for any value b > 0,

(b) If X is a random variable with finite mean μ and variance σ2 , then for any value k > 0,

Hint: use the result given in Part (a). (20%)

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