Understanding $\frac {b^{n+1}-a^{n+1}}{b-a} = \sum_{i=0}^{n}a^ib^{n-i}$ I'm going through a book about algorithms and I encounter this.
$$\frac {b^{n+1}-a^{n+1}}{b-a} = \sum_{i=0}^{n}a^ib^{n-i}$$
How is this equation formed? If a theorem has been applied, what theorem is it?
[Pardon me for asking such a simple question. I'm not very good at maths.]

Multiply both sides by b-a, watch for the cancling of terms, and you will have your answer.
