Hi all, I am so sorry I don't know whether to post this. I am revising Proof by mathematical induction Further maths using an Edexcel FP1 book. The following is from chapter 6 example 3. I know how to work Proof by mathematical induction it is part of the example that I don't understand. I don't know how the series notation becomes to equal to the highlighted part. http://www.mathsrev.com/wp-content/uploads/Proof-by-mathematical-induction.png [Broken] The problem here is "r is a power" and I have not meant problems where r is a power and the book does not explain so much about that. Thanks for the help.