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**debjit625****Member**- Registered: 2012-07-23
- Posts: 89

I can't solve this one ...

Find n ,if

Thanks

*Last edited by debjit625 (2012-12-03 20:08:48)*

Debjit Roy

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The essence of mathematics lies in its freedom - Georg Cantor

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 85,362

Hi;

n = 49.

Solve this:

(n+2)(n+1) = 2550

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,336

hi debjit625

So you just need to solve

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**debjit625****Member**- Registered: 2012-07-23
- Posts: 89

Ok I have seen this in my book too but ,I didn't understood how

expands into ,is their any special rules or am I missing something very basicDebjit Roy

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The essence of mathematics lies in its freedom - Georg Cantor

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 85,362

Hi;

(n+2)! = (n+2)(n+1)**n (n-1)(n-2)(n-3)...1**

n! =**n (n-1)(n-2)(n-3)...1**

(n+2)! = (n+2)(n+1)**n!**

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

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**debjit625****Member**- Registered: 2012-07-23
- Posts: 89

Now I got it thanks guys, it was so simple ,my book didnt have enough of factorials its more about permutation can you guys give me some resource on factorials...

Thanks

Debjit Roy

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The essence of mathematics lies in its freedom - Georg Cantor

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 85,362

Hi;

In order of difficulty.

http://www.mathsisfun.com/numbers/factorial.html

http://www.purplemath.com/modules/factorial.htm

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

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**debjit625****Member**- Registered: 2012-07-23
- Posts: 89

I know about mathisfun ,I meant some advance stuff

Thanks again...

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The essence of mathematics lies in its freedom - Georg Cantor

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 85,362

Hi;

Please check post #7, they get more and more difficult.

Of course that result can be rigorously obtained, but who cares?

Combinatorics is Algebra and Algebra is Combinatorics.

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**debjit625****Member**- Registered: 2012-07-23
- Posts: 89

Thanks bobbym for the link http://www.themathpage.com/aprecalc/factorial.htm

as I was searching factorial problems involving variables and it had some great stuff.

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The essence of mathematics lies in its freedom - Georg Cantor

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 85,362

Hi debjit625;

You are welcome.

Of course that result can be rigorously obtained, but who cares?

Combinatorics is Algebra and Algebra is Combinatorics.

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