Question

设DX=4,DY=2且X与Y独立,则D（3X-2Y）=?

Answer 1

因为X与Y相互独立,D(aX+bY)=a^2D(X)+b^2D(Y),D(aX-bY)=a^2D(X)+b^2D(Y),D(3X-2Y)=9D(X)+4D(Y)=36+8=44