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# If root(3x + 4) = x, what is the value of x?

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Intern
Joined: 14 Oct 2014
Posts: 19
If root(3x + 4) = x, what is the value of x?  [#permalink]

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Updated on: 12 Mar 2015, 05:29
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91% (00:49) correct 9% (01:20) wrong based on 132 sessions

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If $$\sqrt{3x+4} = x$$, what is the value of x?

A. -4
B. -2
C. 1
D. 2
E. 4

Originally posted by zatspeed on 11 Mar 2015, 20:31.
Last edited by Bunuel on 12 Mar 2015, 05:29, edited 4 times in total.
Renamed the topic, edited the question and added the OA.
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Re: If root(3x + 4) = x, what is the value of x?  [#permalink]

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11 Mar 2015, 20:52
3
zatspeed wrote:
if (root)3x+4 = x, what is the value of x?

1) -4
2) -2
3) 1
4) 2
5) 4

Is the answer 1 or 4?

The answer is 4.

$$\sqrt{3x+4} = x$$
Squaring both sides, $$3x+4 = x^2$$
Solving this quadratic, you get (x-4)(x+1) = 0
x = 4 or -1

Anyway, if you have confusion in what will satisfy a given equation, just plug in to check.
If you put x = 1 in $$\sqrt{3x+4} = x$$, it doesn't satisfy. If you put x = 4, it does.
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Re: If root(3x + 4) = x, what is the value of x?  [#permalink]

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11 Mar 2015, 21:51
1
Hi Bunuel (and/or other Moderators),

Can someone go in and place a 'square-root sign' into the original prompt (and the title if possible). In it's current format, the prompt isn't completely clear, and I doubt that a typical site visitor would recognize the 'intent' of this question.

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Joined: 07 Feb 2015
Posts: 45
Re: If root(3x + 4) = x, what is the value of x?  [#permalink]

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11 Mar 2015, 23:24
sqrt(3x+4)=x
from the question itself we can deduct that x>=0
squaring ,x^2-3x-4=0
x=4,-1
neglecting negative vaue , x=4
(E)
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Re: If root(3x + 4) = x, what is the value of x?  [#permalink]

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12 Mar 2015, 05:29
EMPOWERgmatRichC wrote:
Hi Bunuel (and/or other Moderators),

Can someone go in and place a 'square-root sign' into the original prompt (and the title if possible). In it's current format, the prompt isn't completely clear, and I doubt that a typical site visitor would recognize the 'intent' of this question.

GMAT assassins aren't born, they're made,
Rich

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Done.
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Re: If root(3x + 4) = x, what is the value of x?   [#permalink] 12 Mar 2015, 05:29

# If root(3x + 4) = x, what is the value of x?

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