Question

已知EX=-1,DX=3,则E[2(X^2-1]=

Answer 1

因为

D(X)=E(X^2)-E^2(X)

所以 E(X^2)=D(X)+E^2(X)=3+1=4

故 E(2(X^2-1)]=E(2X^2-2)

=2E(X^2)-E(2)

=2*4-2

=6