# Math Help - sum of squares

1. ## sum of squares

Suppose we want to find a closed formula for the sum of the $N$ squares. Start with the formula $\sum_{n=0}^{N} x^n = \frac{x^{N+1}-1}{x-1}$. Then do we do the following:

$\sum_{n=0}^{N} (xD)^n = \frac{(xD)^{N+1}-1}{(xD)-1}$

e.g. apply the $(xD)^2$ operator?

2. What do you call an (xD)² operator ?

And yes the second formula is correct too...