FP1 Factorials help

Hey!

I've come across this whilst doing some ocr fp1 papers, and wondered if anyone could point me in the right direction? I can never seem to get my head round these sorts of questions when involving factorials!

Many thanks,
Klaxoii





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I'm not sure if you've made any progress but a good first step if you're not confident with these questions is to expand the factorials:

$\displaystyle (r+2)!-(r+1)!$

$\displaystyle = \left[(r+2)\times(r+1)\times r \times... \times 2 \times 1\right] - \left[(r+1)\times r \times ... \times 2 \times 1\right]$

The next step is to factorise. Can you continue from here? Post all your working/ideas if you get stuck.

Thanks for the fast reply, is this correct? I think i've got it..





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