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04 May 2015, 12:20
Kudos
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i) \(x^2 + y^2 = 2xy\)
\((x-y)^2 = x^2 + y^2 - 2xy\)
since \(x^2 + y^2 = 2xy\)
=> \((x-y)^2 = 2xy - 2xy\)
=> x-y = 0
ii) \(x^2+y^2 = 0\)
=> \(x^2 = - y^2\)
since \(y^2\) can not be negative and also \(x^2\) can not be negative
=> x = y = 0
so D
\((x-y)^2 = x^2 + y^2 - 2xy\)
since \(x^2 + y^2 = 2xy\)
=> \((x-y)^2 = 2xy - 2xy\)
=> x-y = 0
ii) \(x^2+y^2 = 0\)
=> \(x^2 = - y^2\)
since \(y^2\) can not be negative and also \(x^2\) can not be negative
=> x = y = 0
so D
05 May 2015, 01:32
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What is the value of x - y ?
(1) 2xy - y^2 = x^2 --> rearrange: x^2 -2xy + y^2 = 0 --> (x - y)^2 = 0 --> x - y =0. Sufficient.
(2) y^2 = -x^2 --> rearrange: y^2 + x^2 = 0 --> the sum of two non-negative values can be zero only if both are 0. Thus x = y = 0 --> x - y = 0. Sufficient.
Answer: D.
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(1) 2xy - y^2 = x^2 --> rearrange: x^2 -2xy + y^2 = 0 --> (x - y)^2 = 0 --> x - y =0. Sufficient.
(2) y^2 = -x^2 --> rearrange: y^2 + x^2 = 0 --> the sum of two non-negative values can be zero only if both are 0. Thus x = y = 0 --> x - y = 0. Sufficient.
Answer: D.
Similar questions to practice:
what-is-the-difference-of-the-integers-m-and-n-154567.html
what-is-the-value-of-ab-151880.html
what-is-the-sum-of-integers-a-and-b-1-a-b-2-b-47089.html
is-xy-132217.html
is-x-y-134781.html
is-x-y-108977.html
is-x-y-185979.html
Hope it helps.
