Problem Solving

wait what?

something is seriously wrong here, as elementary number picking is quick to show.

first off, the 2's clearly cancel, so get rid of them.

if we let x = 2 and y = 1/2, then the expression is (5/2)^2 / (3/2)^2, which is 25/9 = 2.77777..., an answer that is clearly not listed. worse yet, plugging in other numbers leads to other answer choices.

incidentally, the only numbers that satisfy the initial constraint (xy = 1) and actually give the answer 16 are plus or minus (√15)/5 and (√15)/3 - two numbers that, i can confidently say, no one is going to pick anytime soon.

wait, uh, well, i made up a problem that looks at least somewhat like this one, with the desired solution.

here you go:

simplyjat wrote:This question is a mistake in GMATPrep, The original intent of the question is to ask

If XY = 1
Than what is the value of (2^[(x+y)^2])/(2^[(x-y)^2]) ?
Which simplifies to
(2^(x^2))*(2^(y^2))*(2^(2xy)) / (2^(x^2))*(2^(y^2))*(2^(-2xy))
=> (2^(2xy)) / (2^(-2xy))
=> (2^(4xy))
=> (2^(4*1))
=> 2^4
=> 16

that's awesome

where'd you get the fix? did you figure it out yourself?