How Do You Differentiate the Power Series g(x) = Σ 2x²ⁿ?

[blak97]

Homework Statement

Explicitly compute the function g defined by:
g(x) = $\Sigma$n²x²ⁿ from n=1 to infinity


I was thinking something along the lines of differentiating$\Sigma$ x²ⁿ twice

 

[micromass]

Yes. So what do you get??