Mathematical expectation property E(C)=C E(CX)=CE(X)

e( 1/2x^2- 1)=2= 1/2e(x^2)- 1

So e (x 2) = 6.

According to the property of variance d (ax+b) = a 2d (x)

d( 1/2X- 1)= 1/2

So D(X)=2.

Because d (x) = e (x 2)-[e (x)] 2.

So e (x) = [e (x 2)-d (x)] (1/2) = 2.