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If a = (x + y)2 and b = x2 + y2 and xy > 0, which of the fol [#permalink]
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Expert's post 00:00

Question Stats: 77% (00:10) correct 22% (00:04) wrong based on 9 sessions
If $$a = (x + y)^2$$ and $$b = x^2 + y^2$$ and $$xy > 0$$, which of the following must be true?
Indicate all such statements.

A. a = b
B. a > b
C. a is positive
[Reveal] Spoiler: OA

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Re: If a = (x + y)2 and b = x2 + y2 and xy > 0, which of the fol [#permalink]
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expanding a we get, a = $$x^2 + y^2 + 2xy$$
b = $$x^2 + y^2$$
Since $$xy$$ > 0; $$2xy$$ > $$0$$
therefore a is greater than b by $$2xy$$; Hence option a is not correct but option b is correct

we know square of any number is always +ve hence$$x^2 + Y^2$$ is +ve and when it is added to $$2xy$$ the result is +ve
option c is also correct.

Hence only option b and c are correct.
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This is my response to the question and may be incorrect. Feel free to rectify any mistakes
Need Practice? 20 Free GRE Quant Tests available for free with 20 Kudos Re: If a = (x + y)2 and b = x2 + y2 and xy > 0, which of the fol   [#permalink] 20 Jun 2018, 01:12
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# If a = (x + y)2 and b = x2 + y2 and xy > 0, which of the fol  Question banks Downloads My Bookmarks Reviews Important topics Powered by phpBB © phpBB Group Kindly note that the GRE® test is a registered trademark of the Educational Testing Service®, and this site has neither been reviewed nor endorsed by ETS®.