f(x^2)=f(x)^2 ?

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Source: — Data Sufficiency |

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by Brent@GMATPrepNow » Sun Jun 02, 2013 6:21 am
himu wrote:If x > 0, does f(x^2) = f(x)^2 ?

(1)f(x)=√x

(2)x=9
Target question: Does f(x^2) = f(x)^2 ?

Statement 1: f(x)=√x
Since we now know what the function looks like, the target question is now . . .
Does √(x^2) = (√x)^2 ?
The answer to this question is YES.
If x > 0, then √(x^2) definitely equals (√x)^2
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: x=9
Since we don't know anything about the function f, we cannot answer the target question with certainty.
So statement 2 is NOT SUFFICIENT

Answer = A

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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