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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