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#### Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here. # If x + 2y = a and x – 2y = b, which of the following express  Question banks Downloads My Bookmarks Reviews Important topics
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Founder  Joined: 18 Apr 2015
Posts: 12642
Followers: 269

Kudos [?]: 3178 , given: 11677

If x + 2y = a and x – 2y = b, which of the following express [#permalink]
Expert's post 00:00

Question Stats: 75% (02:05) correct 25% (01:32) wrong based on 32 sessions
If $$x + 2y = a$$ and $$x – 2y = b$$, which of the following expressions is equal to $$xy$$?

A. $$ab$$

B. $$\frac{a+b}{2}$$

C. $$\frac{a-b}{2}$$

D. $$\frac{a^2-b^2}{4}$$

E. $$\frac{a^2-b^2}{8}$$
[Reveal] Spoiler: OA

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GRE Prep Club Members of the Month: Each member of the month will get three months free access of GRE Prep Club tests. Intern Joined: 24 Jan 2019
Posts: 1
Followers: 0

Kudos [?]: 1  , given: 0

Re: If x + 2y = a and x – 2y = b, which of the following express [#permalink]
1
KUDOS
elimination is the best way to solve it,
options (b) and (c) is eliminated as they have solution only in terms of x, not xy which the question is about. Thus they are eliminated
for last 2 option, evaluate a^2-b^2 which is 8xy. Therefore, option d is the correct answer
Founder  Joined: 18 Apr 2015
Posts: 12642
Followers: 269

Kudos [?]: 3178 , given: 11677

Re: If x + 2y = a and x – 2y = b, which of the following express [#permalink]
Expert's post
$$x=a-2y$$ and $$x=b+2y$$

$$a-2y=b+2y$$

$$a-b=4y$$

$$y=\frac{a-b}{4}$$

$$2y=a-x$$

$$2y=x-b$$

$$a-x=x-b$$

$$x=\frac{a+b}{2}$$

$$x \times y$$

$$\frac{a-b}{4} \times \frac{a+b}{2}$$

$$\frac{(a-b)^2}{8}$$

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GRE Prep Club Members of the Month: Each member of the month will get three months free access of GRE Prep Club tests. Re: If x + 2y = a and x – 2y = b, which of the following express   [#permalink] 26 Jul 2020, 11:05
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