Originally Posted by

**james121515** Thanks for your replies.

The question is worded exactly as in the original post, except for a small typo on my part it should have been:

(b) $\displaystyle f_Y(y)$ and not $\displaystyle f_y(y)$

If the wording of the problem is correct, could you please help me understand the question. Since our pdf $\displaystyle f_R(x)$ is for the random variable $\displaystyle R$, woudn't we need some relationship between $\displaystyle R$ and $\displaystyle X$, and then from $\displaystyle X$ to $\displaystyle Y$ (which we have since $\displaystyle Y=X^3$) in order to do this?

Best,

James