equalities-need help understanding

BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

grandh01: Master | Next Rank: 500 Posts; Posts: 265; Joined: Tue Jul 03, 2012 11:04 pm; Followed 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.

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 am; Location: Chicago, IL; Thanked: 36 times; Followed by:7 members

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

Skype / Chicago quant tutor in GMAT / GRE
https://gmat.tutorchicago.org/

• Page 1 of 1