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# (FP2) How is r! a factor of (r+1)!

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Why bother with a post grad course - waste of time? 17-10-2016
1. So in this question in series in FP2

Simplify

And apparently this goes to

As is the common denominator

I do not understand how this is the case? Any help appreciated!
2. (Original post by Music With Rocks)
So in this question in series in FP2

Simplify

And apparently this goes to

As is the common denominator

I do not understand how this is the case? Any help appreciated!
What can be expanded into?
3. (Original post by Slowbro93)
What can be expanded into?
?
4. (Original post by Music With Rocks)
?
Okay, let's go back on step:

How do you calculate: and
5. surprised that this is a Further maths question.
(r+1)!=(r+1) x r! which makes r! a factor
take the example:
4! = 4 x 3!
so 3! is a factor of 4!
I dont do further maths btw
6. (Original post by Slowbro93)
Okay, let's go back on step:

How do you calculate: and
ohhhhhhh...

so is which is the same as

So then is

Is this correct?
7. (Original post by Music With Rocks)
ohhhhhhh...

so is which is the same as

So then is

Is this correct?
Agreed!

Now can you see what you have to do?
8. (Original post by Nayzar)
surprised that this is a Further maths question.
(r+1)!=(r+1) x r! which makes r! a factor
take the example:
4! = 4 x 3!
so 3! is a factor of 4!
I dont do further maths btw
Didn't see your reply as I was busy typing mine out haha, thank you that makes sense.
9. (Original post by Nayzar)
I dont do further maths btw
savage
10. (Original post by Slowbro93)
Agreed!

Now can you see what you have to do?
so that means that is a multiple of so therefore is the common denominator

I get it now, thank you very much
11. (Original post by Nayzar)
surprised that this is a Further maths question.
(r+1)!=(r+1) x r! which makes r! a factor
take the example:
4! = 4 x 3!
so 3! is a factor of 4!
I dont do further maths btw
Oh and it is only a part of a question not a question in itself they wouldn't want it to be nice...
12. (Original post by Alexion)
savage
lol nah i didnt mean it like that haha

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