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# FP1 Series help please. Watch

1. Just a quick show that:

1/r! - 1/(r+1)! = r/(r+1)!

It's only 2 marks so I know I'm missing something, can anybody point me in the right direction?

I'm aware you've likely got to get a common denominator but i'm not sure the best way of doing it.

Thanks.
2. (Original post by Outsanity)
Just a quick show that:

1/r! - 1/(r+1)! = r/(r+1)!

It's only 2 marks so I know I'm missing something, can anybody point me in the right direction?

I'm aware you've likely got to get a common denominator but i'm not sure the best way of doing it.

Thanks.

Note that .
That should be enough to get you on the way.
3. (Original post by Get me off the £\?%!^@ computer)
Ahh cheers, never occurred to me to put the (r+1) on the top line to make it cancel, knew I was missing a trick!

Thanks so much

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