# Question: Express var X Y var X Y and cov X

Express var(X + Y), var(X – Y), and cov(X + Y, X – Y) in terms of the variances and covariance of X and Y.

## Answer to relevant Questions

If var(X1) = 5, var(X2) = 4, var(X3) = 7, cov(X1, X2) = 3, cov(X1, X3) = –2, and X2 and X3 are independent, find the covariance of Y1 = X1 – 2X2 + 3X3 and Y2 = –2X1 + 3X2 + 4X3. Find the expected value of the discrete random variable X having the probability distribution f(x) = |x – 2| / 7 for x = –1, 0, 1, 3 With reference to Exercise 3.101 on page 108, find E(PS), the expected receipts for the commodity. With reference to Exercise 4.71, what can we assert about the amount of time it takes a person to be served at the given restaurant if we use Chebyshev’s theorem with k = 1.5? What is the corresponding probability rounded ...(a) If X takes on the values 0, 1, 2, and 3 with probabilities 1/125, 12/125, 48/125 , and 64/125 , find E(X) and E(X2). (b) Use the results of part (a) to determine the value of E[(3X + 2)2].Post your question