How do I calculate the elastic potential energy stored in a spring?

[lilmul123]

This is my first time here! Thanks for the help in advance.

The staples inside a stapler are kept in place
by a spring with a relaxed length of 0.115 m.
If the spring constant is 45.0 N/m, how
much elastic potential energy is stored in the
spring when its length is 0.145 m? Answer in
units of J.

I know I have to use F=kx (maybe), but what's confusing me is the potential energy part. How do I fit that into finding the answer?

 

[Amith2006]

elastic P.E = work done to compress =integral of [(F)x(dx)] between the limits 0.145 and 0.115

 

[Dick]

If you haven't done calculus, the result Amith2006 is pointing you toward can be written PE=(1/2)*k*x^2, where x is the displacement from equilibrium.

 

[lilmul123]

Yeah, I've done calculus, but thank you both!