Q1. Let f(x; y) = 2e^-x-y, 0 < x<= y < 무한대, be the joint pdf of X and Y .
Answer each of the following questions.
1. fX(x)
2. fY (y)
3. fXjY (xjy)
4. fY jX(yjx)
5. E(Xjy)
6. E[E(Y jx)]
7. Var(X)
8. Var(Y )
9. Cov(X; Y )