Hi Vincen,
We're told that X and Y are integers. We're asked if X^7 is less than 6^Y. This is a YES/NO question. We can solve it by TESTing VALUES and/or by using Number Property rules. To start, it's worth nothing that X^7 could be positive (if X is positive), 0 (if X is 0) or negative (if X is negative). However, 6^Y can ONLY be positive (regardless of the value of Y)...
1) X^3 = -125
Fact 1 tells us that X will be NEGATIVE (you don't technically have to calculate it, but the one solution to this equation is X = -5). Since X is negative, X^7 will also be negative. Since 6^Y is always positive, the answer to the question is ALWAYS YES.
Fact 1 is SUFFICIENT.
2) Y^2 = 36
The equation in Fact 2 has two solutions: +6 and -6. However, we know nothing about the value of X. Since X^7 could be negative or a gigantic positive number, the answer to the question could be YES or NO.
Fact 2 is INSUFFICIENT.
Final Answer: A
GMAT assassins aren't born, they're made,
Rich
If x and y are integers, is x^7 < 6^y?
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