cypherskull wrote:Thanks Anil and Anurag. I do have a question though (and excuse me if u find it silly but this part really confuses me). Somewhere in this forum I read that on the GMAT, we should consider sq. root of a positive number to be a positive value only. Got no second thoughts now that I'm wrong, but am I missing something here? In which scenario does that rule apply?
If k is a positive number, then √k means
by definition "the positive square root of k". So √k can never be negative, because of the way the square root symbol is defined.
So if you see the expression √16, that cannot be negative, and so certainly must be equal to 4 and nothing else. But there are still two different numbers whose square is 16: 4 and -4. So if there's no square root symbol in your expression to rule out the negative solution, the negative solution will very often be perfectly legitimate. An equation like x^2 = 16 has two perfectly good solutions for x, for example. Or if you know a^2 = b^2, you cannot be sure that a = b; it might be that a = -b.
