For which of the following values of x is the equation : Quant Question Archive [LOCKED]
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# For which of the following values of x is the equation

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Intern
Joined: 03 Apr 2006
Posts: 46
Followers: 0

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For which of the following values of x is the equation [#permalink]

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09 Jun 2007, 15:15
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

For which of the following values of x is the equation (x+4)!/x!= (x + 1)! true?

6

7

8

9

10
Director
Joined: 13 Mar 2007
Posts: 545
Schools: MIT Sloan
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Kudos [?]: 70 [0], given: 0

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09 Jun 2007, 16:03
(A)

did nothing great - just substitued the value and it worked !

is there any other way?
CEO
Joined: 17 May 2007
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Kudos [?]: 581 [0], given: 210

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09 Jun 2007, 18:19
You can simplify a little bit.

(x+4)! / x! can be written as (x+4)(x+3)(x+2)(x+1) --> LHS
(x+1)! = (x+1)(x)(x-1).... (1) --> RHS and u can cancel out (x+1)
so now the equation looks like :
(x+4)(x+3)(x+2) = x!

Pluggin in values is slightly easier now. Answer is still 6

which is A
09 Jun 2007, 18:19
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