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If 2x + y = –31, what is the value of x?

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If 2x + y = –31, what is the value of x? [#permalink]

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New post 14 May 2017, 11:02
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A
B
C
D
E

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70% (01:03) correct 30% (00:53) wrong based on 28 sessions

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Re: If 2x + y = –31, what is the value of x? [#permalink]

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New post 14 May 2017, 13:14
2x + y = –31, x = ?

(1) (y − 2)(y − 2) − 4 = 0
=> y^2 - 4 - 4 = 0
=>y^2 = 8
=> y = ±2√2

So, either x = (-31 + 2√2)/2 or x = (-31 - 2√2)/2;
Hence, Insufficient.

(2) y = 2; Sufficient.
Answer B.
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Re: If 2x + y = –31, what is the value of x? [#permalink]

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New post 15 May 2017, 09:30
(y-2)(y-2)-4=0
Y^2-4y+4-4=0
Y(y-4)=0
So either y=0 or 4
Hence insufficient
Y=2
Clearly sufficient
Hence B

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Re: If 2x + y = –31, what is the value of x? [#permalink]

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New post 15 May 2017, 12:52
saswata4s wrote:
2x + y = –31, x = ?

(1) (y − 2)(y − 2) − 4 = 0
=> y^2 - 4 - 4 = 0
=>y^2 = 8
=> y = ±2√2
.


Although you get answer right, statement one has a problem. You deal with as difference of squares while it is not. You are right if it is (y − 2)(y + 2).
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Re: If 2x + y = –31, what is the value of x? [#permalink]

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New post 15 May 2017, 12:55
If 2x + y = –31, what is the value of x?

(1) (y − 2)(y − 2) − 4 = 0

(y-2)^2 = 4

y-2 = +/- 2

y= 4 or y =0

Therefore, x has 2 answers

Insufficient

(2) y = 2

Apply in equation in prompt..........x has one answer

Sufficient

Answer: B
Re: If 2x + y = –31, what is the value of x?   [#permalink] 15 May 2017, 12:55
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If 2x + y = –31, what is the value of x?

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