If ax² + bx³ = 5, where a and b are non-zero numbes, what is the value of a + b? (1) ax² = a (2) bx³ = b

The possible value of X is +/-1 from the first condition. Therefore if we proceed ahead with this without leaving it here, there will be 2 equations for a and b : a + b equal to 5 and a – b equal to 5. Solving both these equations, we get the value of a + b equal to 5. So even option A is sufficient.

The important thing to remember here is that, when a number is squared, it will always result in a positive, regardless of whether the original number was negative or positive. This is not the case with a number that is cubed. A cube will only be positive if the original integer was positive; otherwise, it will be negative. That having been said, statement (1) is insufficient. While we know that X can be nothing other than 1 or –1 in order for ax^2to equal a, we are not told specifically if X is 1 or –1. Statement (2), however, is sufficient. Because X is cubed, we know that it had to be 1 from the beginning. Statement (2) tells us that a + b = 5

Users browsing this forum: No registered users and 2 guests

You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot post attachments in this forum

GMAT(TM) and GMAT CAT (TM) are registered trademarks of the Graduate Management Admission Council(TM). The Graduate Management Admission Council(TM) does not endorse, nor is affiliated in any way with the owner or any content of this site.