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What is the value of x^2 – y^2 ?

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What is the value of x^2 – y^2 ? [#permalink]

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New post 24 Jun 2017, 07:34
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A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

68% (01:04) correct 32% (01:48) wrong based on 78 sessions

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Re: What is the value of x^2 – y^2 ? [#permalink]

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New post 24 Jun 2017, 09:57
IMO C

From both we can find that x=4y
putting value back to statement 2 will give y=+/- 1

since we are asked square of x - square of y, no matter what the sign we will get the same result.

waiting for OA

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Re: What is the value of x^2 – y^2 ? [#permalink]

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New post 24 Jun 2017, 10:46
Answer : C

From Statement 1, (x–y)(2x+y)=9 => 2x^2-xy-y^2 = 9. Clearly Insufficient.

From Statement 2, y(x–y)=3 => xy-y^2 = 3. Clearly Insufficient.

Combining Both statement, i.e substituting statement 2 in statement 1,

xy = 3+y^2 ------ from statement 2,

2x^2-(3+y^2)-y^2 = 9 => 2x^2-2y^2=12,

Solving, x^2-y^2 = 6. Hence, Answer C.

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Re: What is the value of x^2 – y^2 ? [#permalink]

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New post 21 Sep 2017, 22:44
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C.

Stmt-1: \((x-y)(2x+y)=9\)

Stmt-2: \(y(x-y)=3 => 3y(x-y)=9\) (Multiplied both sides by 3)

From stmt 1 and 2, we can say
\(3y(x-y)=(x-y)(2x+y)
=> 3y=(2x+y) => x=y\)

\(∴ x^2 – y^2=0\)
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Hasan Mahmud

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Re: What is the value of x^2 – y^2 ? [#permalink]

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New post 21 Sep 2017, 23:30
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(1) Unsuf.
(2) Unsuf.
(1) & (2) х=у but it doesn't satisfy (1) (0=9)
Unsuf.
Answer E

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Re: What is the value of x^2 – y^2 ?   [#permalink] 21 Sep 2017, 23:30
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