Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:
Re: a GWD math (6) , which hasn't been discussed [#permalink]
20 Aug 2011, 16:15
Rephrase the question: "x = y?"
Statement 1: x^2 = y^2 implies that |x| = |y|. In the xy-plane this looks like an X (two lines) straight through the origin with slopes of 1 and -1. For xy < 0 (quadrants II and IV), y = -x. For xy > 0 (quadrants I and III), y = x.
If |x| = |y|, x does not have to equal y, it could equal -y. Insufficient.
Statement 2: xy > 0 means that any point occupies either quadrant I or III. x and y could take on any coordinate in these quadrants, such as (4,3), (1000000000000,1), (-452, -2), or (1,1), (-55,-55) etc. We do not know whether x and y are equal. Insufficient.
Combined: |x| = |y| and xy > 0, so x = y. Sufficient.