f(x) = ∫ [-x,x] f(x,y)dy = 2x, 0 E(X) = ∫ [0,1] 2x^2dx = 2/3. f(y) = ∫ [|y|,1] f(x,y)dx = 1-|y|, -1 E(Y) = 0. ( f(y) = f(-y) ) E(Z) = E(2X+Y) = 2E(X)+E(Y) = 2(2/3)+0 = 4/3 D(Z) = 4D(X)+D(Y) 你会了吧?
E(X) = ∫ [0,1] 2x^2dx = 2/3.
f(y) = ∫ [|y|,1] f(x,y)dx = 1-|y|, -1 E(Y) = 0. ( f(y) = f(-y) ) E(Z) = E(2X+Y) = 2E(X)+E(Y) = 2(2/3)+0 = 4/3 D(Z) = 4D(X)+D(Y) 你会了吧?
E(Y) = 0. ( f(y) = f(-y) )
E(Z) = E(2X+Y) = 2E(X)+E(Y) = 2(2/3)+0 = 4/3
D(Z) = 4D(X)+D(Y) 你会了吧?
