Need help understanding what the problem is asking for

This topic has expert replies
Source: — Data Sufficiency |

Master | Next Rank: 500 Posts
Posts: 153
Joined: Tue Jun 02, 2009 2:48 pm
Location: Ohio
Thanked: 16 times
virtuoso902 wrote:Hey everyone. I Don't completely understand what this question is asking for. Also what is the most efficient way to solve this problem? Thank you ahead of time!

What is the value of X^2-Y^2?

1) x-y=0

2) x+y=4

The answer is:

A
x^2 - y^2 = (x + y) (x - y)

1. if x-y = 0

(x + y) (x - y)
(x + y) * 0 = always equals 0 Suff

2. if x+y = 4

(x + y) (x - y)
4 * (x-y)

InSuff.