# casella

1. ### How to prove Var(xy)=E[x]^2*var(y)+E[y]^2*var(x)+var(x)*var(y)

I want to prove above-mentioned formula using following formula: Var(y)=Ex[var(y/x)]+varx[E(y/x)] In next step I want to prove the title-mentioned formula using Taylor series expansion.