E(2X²+6) = 2E(X²)+E(6) =2E(X²)+6
而 D(X) = E(X²)-(E(X))²,即 4= E(X²)-(-2)² =E(X²)-4
得 E(X²)-=8
所以E(2X²+6) =16+6=22那求E【2（X的平方-3）】呢？E(2(X²-3))E(2X²-6) = 2E(X²)+E(-6) =2E(X²)-6而 D(X) = E(X²)-(E(X))²，即 4= E(X²)-(-2)² =E(X²)-4得 E(X²)-=8所以E(2X²+6) =16-6=10