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#### Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here. # If 0.5(y − x) = −1 and x2 − y2 = 24, what is the sum of x  Question banks Downloads My Bookmarks Reviews Important topics
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GRE Prep Club Legend  Joined: 07 Jun 2014
Posts: 4857
GRE 1: Q167 V156 WE: Business Development (Energy and Utilities)
Followers: 105

Kudos [?]: 1782 , given: 397

If 0.5(y − x) = −1 and x2 − y2 = 24, what is the sum of x [#permalink]
Expert's post 00:00

Question Stats: 100% (00:45) correct 0% (00:00) wrong based on 5 sessions
If 0.5(y − x) = −1 and $$x^2 - y^2 = 24$$, what is the sum of x and y ?
A. −48
B. −12
C. 6
D. 12
E. 48

Drill 2
Question: 6
Page: 497-498
[Reveal] Spoiler: OA

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Sandy
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GRE Prep Club Legend  Joined: 07 Jun 2014
Posts: 4857
GRE 1: Q167 V156 WE: Business Development (Energy and Utilities)
Followers: 105

Kudos [?]: 1782 , given: 397

Re: If 0.5(y − x) = −1 and x2 − y2 = 24, what is the sum of x [#permalink]
Expert's post
Explanation

Know your common quadratics. You are asked for the value of x + y.

Because $$x^2 - y^2 =(x + y)(x - y) = 24$$, if the value of (x − y) is found, (x + y) can be figured out.

Manipulate the equation 0.5(y − x) = –1 to get (y − x) = –2.

Multiplying both sides by –1, you get x – y = 2.

Substitute this value into the equation (x + y)(x – y) = 24 and then divide both sides of the equation by 2 to get (x + y) = 12. The answer is choice (D).
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Sandy
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Try our free Online GRE Test Re: If 0.5(y − x) = −1 and x2 − y2 = 24, what is the sum of x   [#permalink] 18 Mar 2018, 07:02
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