I think this explanation is incorrect in GMAT CAT

[alex85]

See question below, says X can be either 0 or 1, i think it can be only 1 due to condition given in the prompt, the answer is still E though.

If ab ≠ 0, does a = b?

(1) x^a = x^b
(2) x = x^2

(1) INSUFFICIENT: If xa = xb, there are two possibilities. The first possibility is that x is any number other than 0 and 1, in which case a = b must be true. The other possibility is that x is either 0 or 1. If x is 0 or 1, then a and b could be anything, because 1 raised to any power is 1, and 0 raised to any power is 0. If x is 0 or 1, you would not be able to tell if a = b.

(2) INSUFFICIENT: This statement indicates nothing about a or b.

(1) AND (2) INSUFFICIENT: Whereas the second statement indicates nothing about a or b, it does indicate that x is either 0 or 1. There is no way to tell whether a = b is true.

The correct answer is E.

[tim]

No, there is no reason x can't be 0. Neither a nor b can be 0, but the prompt says nothing about x.

[alex85]

oh right... makes sense

[RonPurewal]

ok. any other questions, go ahead and ask.