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# If x – y = and x2 – y2 = 3, what is the value of x + y?

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Retired Moderator
Joined: 07 Jun 2014
Posts: 4803
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 173

Kudos [?]: 2971 [1] , given: 394

If x – y = and x2 – y2 = 3, what is the value of x + y? [#permalink]  23 Jun 2018, 11:50
1
KUDOS
Expert's post
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Question Stats:

100% (00:20) correct 0% (00:00) wrong based on 31 sessions
If $$x - y = \frac{1}{2}$$ and $$x^2 - y^2 = 3$$, what is the value of $$x + y$$?

[Reveal] Spoiler: OA
6

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Sandy
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Intern
Joined: 05 Jan 2018
Posts: 32
Followers: 0

Kudos [?]: 20 [0], given: 8

Re: If x – y = and x2 – y2 = 3, what is the value of x + y? [#permalink]  25 Jun 2018, 07:02
Ans. 6
Retired Moderator
Joined: 07 Jun 2014
Posts: 4803
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 173

Kudos [?]: 2971 [0], given: 394

Re: If x – y = and x2 – y2 = 3, what is the value of x + y? [#permalink]  28 Jul 2018, 16:09
Expert's post
Explanation

The Difference of Squares (one of the “special products” you need to memorize for the exam) is $$x^2 - y^2 = (x + y)(x - y)$$.

Write this pattern on your paper and plug in the given values, solving for x + y:

$$x^2 - y^2 = (x + y)(x - y)$$
$$3 = (x + y)(\frac{1}{2})$$
$$6 = x + y$$
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Sandy
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Re: If x – y = and x2 – y2 = 3, what is the value of x + y?   [#permalink] 28 Jul 2018, 16:09
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