Abrax99 wrote:

Is x>0?

1) x² = 9x

2) x² = 81

Target question: Is x>0? Statement 1: x² = 9x Rearrange to get: x² - 9x = 0

Factor to get x(x - 9) = 0

So, we have two possible values for x.

Case a: x = 0, in which case

x is NOT greater than 0Case b: x = 9, in which case

x IS greater than 0Since we cannot answer the

target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: x² = 81 Rearrange to get: x² - 81 = 0

Factor to get (x + 9)(x - 9) = 0

So, we have two possible values for x.

Case a: x = -9, in which case

x is NOT greater than 0Case b: x = 9, in which case

x IS greater than 0Since we cannot answer the

target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined Statement 1 tells us that x = 0 or 9

Statement 2 tells us that x = -9 or 9

Since only one value of x satisfies BOTH statements, it MUST be the case that x = 9, which means

x IS greater than 0Since we can answer the

target question with certainty, the combined statements are SUFFICIENT

Answer = C

Cheers,

Brent

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Brent Hanneson – GMATPrepNow.com

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