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DS/ Q 18/PAGE 323/KAPLAN MATH WORKBOOK

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Junior | Next Rank: 30 Posts
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DS/ Q 18/PAGE 323/KAPLAN MATH WORKBOOK

by nonimelb » Sun Mar 29, 2009 8:57 am
For all integers n, n*=n(n-1). What is the value of x*?
(1) x*=x
(2) (x-1)*=x-2

answer choices are usual 1,2,3,4,5

My answer is 4 because I find x=2 and x*=2 in both cases
But Kaplan answer is 2, which I am not convinced with.

Please explain if someone can clarify?
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Source: — Data Sufficiency |
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by ketkoag » Sun Mar 29, 2009 9:21 am
Now here if u take statement 1 then its x^2 - x = x
by solving the above equation u will get x = 0, 2
i.e. insufficient.
Now consider statement 2 i.e. (x-1)(x-2)= x-2
if u solve this question, then u will get x^2 - 4x + 4 = 0
=> (x-2)^2 = 0
=> x = 2 and by this u can calculate unique value of x*. i.e. sufficient.
Hence B.
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Junior | Next Rank: 30 Posts
Posts: 18
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by nonimelb » Mon Mar 30, 2009 8:37 am
thanks for this .
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