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# What is the value of x^2 - y^2? (1) x + y = 2x (2) x + y = 0

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Joined: 02 Sep 2009
Posts: 55277
What is the value of x^2 - y^2? (1) x + y = 2x (2) x + y = 0  [#permalink]

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11 Dec 2018, 07:32
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Difficulty:

35% (medium)

Question Stats:

57% (00:50) correct 43% (00:57) wrong based on 149 sessions

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What is the value of x^2 - y^2?

(1) x + y = 2x
(2) x + y = 0

Project DS Butler: Day 36: Data Sufficiency (DS71)

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Re: What is the value of x^2 - y^2? (1) x + y = 2x (2) x + y = 0  [#permalink]

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11 Dec 2018, 08:01
What is the value of $$x^2 - y^2$$

which simplifies to $$(x+y)*(x-y)$$

So it is obvious that statement 2 is sufficient right away.

But statement 1 is tricky to miss in a hurry.

(1) $$x + y = 2x$$
$$y = x$$

or

$$x - y = 0$$

Hence St 2 is also sufficient.

Hence [color=#00a651]Option (D) is our bet./color]

Best,

Bunuel wrote:
What is the value of x^2 - y^2?

(1) x + y = 2x
(2) x + y = 0

Project DS Butler: Day 36: Data Sufficiency (DS71)

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Re: What is the value of x^2 - y^2? (1) x + y = 2x (2) x + y = 0  [#permalink]

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11 Dec 2018, 08:49
Statement 1:
x + y = 2x
x = y.

x^2 - y^2

= x^2 - x^2

= 0

Sufficient.

Statement 2:

x^2 - y^ 2

= (x+y) (x - Y)
=0 ( x - y)

= 0

Sufficient.

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Joined: 09 Sep 2013
Posts: 11028
Re: What is the value of X^2 -Y^2? 1. x+y=2x 2. x+y=0 I  [#permalink]

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20 Dec 2018, 02:36
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Re: What is the value of X^2 -Y^2? 1. x+y=2x 2. x+y=0 I   [#permalink] 20 Dec 2018, 02:36
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