My professor was going over some powers relating to series, and power series. He came across the problem below which he didn't even know how to solve. I am trying to figure out how to solve it, but can't get anywhere. Does anyone know how to approach this problem? Express this series as a function of x. [tex]\sum n^2x^n [/tex] from n=1 to [tex]\infty[/tex] So, f(x) = ?