Mathematical induction question

[Googl]

Hi all,

I am revising on Proof by mathematical induction and I have came across a question I haven't found a way to work it out.

$$\sum_{r=1}^n r(r!) = (n + 1)! -1$$

I understand the steps of proving by mathematical induction question. The ! is causing the confusion.

 

[mfb]

The ! is causing the confusion.

In which way? It is a Factorial.

 

[Bacle2]

Maybe you can rewrite the general summand as:

(r+1)r!-r! and expand the sum, see what happens.