equalities-need help understanding

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grandh01: Master | Next Rank: 500 Posts; Posts: 265; Joined: Tue Jul 03, 2012 11:04 pmFollowed by: 6 members

by grandh01 » Fri Jul 06, 2012 10:19 am

R= 1 + 2xy + x^2y^2, what is the value of xy?

1) R=0
2) X>0

OA IS A

Thanks in advance.

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Source: Beat The GMAT — Data Sufficiency | Fri Jul 06, 2012 10:19 am

tutorphd: Master | Next Rank: 500 Posts; Posts: 126; Joined: Sun Jun 24, 2012 10:11 amFollowed by: 7 members; Location: Chicago, IL; Thanked: 36 times

by tutorphd » Fri Jul 06, 2012 10:47 am

The problem hinges on recognizing that R is an exact square: R = (1 + xy)^2.

1) R=0 gives xy=-1, sufficient

2) x>0, not sufficient

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https://gmat.tutorchicago.org/

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