1. The problem statement, all variables and given/known data This is my 1st post here, so I will do my best. The following question is part of a number of probability density functions that I have to prove. Once I have the hang of this I should be good for the rest, here is the question: Prove that the following functions are probability density functions: 1/x^2 , x>0 2. Relevant equations 3. The attempt at a solution As I understand to prove a probability density function it must satisfy 1. integral of f(x)dx=1 and 2. must not be negative f(x) for all x I integrate the function of 1/x^2 which is -1/x but I find it tricky to explain myself on how f(x)dx=1 I would be greatfull on pointers on how to prove that the functions is a PDF in a clear manner.