Let XXX have PDF f(x)=12(x+1)f(x) = \frac{1}{2}(x+1)f(x)=21(x+1) for −1≤x≤1-1 \le x \le 1−1≤x≤1. What is E[X2]E[X^2]E[X2]?
13\frac{1}{3}31
12\frac{1}{2}21
712\frac{7}{12}127
23\frac{2}{3}32