So I had a probability test and I couldn't really answer this question. It just asked something like this:
"Considering that $X$ is a random variable, $X$ $\geqslant$ $0$, use the correct inequality to prove what's higher or equal, $E(X^2)^3$ or $E(X^3)^2$.
The only thing I could think was the Jensen's Inequality, but I don't really know how to apply it here.