# Probability Density Function, prove it

1. Homework Statement
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. Homework 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.