Hi, I am a bit confused. Basically if I have a pdf, fX(x) and i want to work out the distribution of Y=X^2 for example, then this involves me letting Y=X^2, rearranging to get X in terms of Y, substituting these into all values of x in my original pdf fX, and then multipying it by whatever dx = . But if i have a pdf fX(x) and just want to work out fX(2x) , this just means put 2x in place of all the x's and that is that. No differentiation etc. Is this right? Thanks a lot - I have an exam tomorrow!