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Math Expert V
Joined: 02 Sep 2009
Posts: 64951
If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?  [#permalink]

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Difficulty:   5% (low)

Question Stats: 91% (01:13) correct 9% (01:04) wrong based on 99 sessions

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If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?

(A) 1
(B) 1/2
(C) 1/3
(D) -1/3
(E) -1/2

Kudos for a correct solution.

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Director  P
Joined: 21 May 2013
Posts: 603
Re: If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?  [#permalink]

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1
Bunuel wrote:
If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?

(A) 1
(B) 1/2
(C) 1/3
(D) -1/3
(E) -1/2

Kudos for a correct solution.

3x^2+x+12x+4=3x^2+x
12x+4=0
x=-1/3
Manager  Joined: 29 Jul 2015
Posts: 150
Re: If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?  [#permalink]

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(x+4)(3x+1) = 3x^2+x

=> 3x^2 + x + 12x +4 = 3x^2 + x
=> 12x+4 = 0
=> 12x = -4
=> x=-1/3

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Concentration: Economics, Finance
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Re: If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?  [#permalink]

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1
Bunuel wrote:
If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?

(A) 1
(B) 1/2
(C) 1/3
(D) -1/3
(E) -1/2

Kudos for a correct solution.

Expand the expression: (x + 4)(3x + 1) = 3x^2 + x to:

3x^2+x+12x+4 = 3x^2 +x , subtract 3x^2 from both sides
13x + 4 = x
12x = -4
x = -1/3

GMAT Club Legend  V
Status: GMATINSIGHT Tutor
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Location: India
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If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?  [#permalink]

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1
Bunuel wrote:
If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?

(A) 1
(B) 1/2
(C) 1/3
(D) -1/3
(E) -1/2

Kudos for a correct solution.

Rearranging the given expression:
(x + 4)(3x + 1) = 3x^2 + x
i.e. 3x^2 + 13x + 4 = 3x^2 + x
i.e. 12x = -4
i.e. x = -4/12 = -1/3

Had it been a difficult expression to solve further, then we could have used options to check which on esatisfies the expression after solving it as further as possible
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Director  B
Status: I don't stop when I'm Tired,I stop when I'm done
Joined: 11 May 2014
Posts: 515
GPA: 2.81
Re: If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?  [#permalink]

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1
Simplifying this equation is my approach here

The equation is

(x + 4)(3x + 1) = 3x^2 + x

or,3x^2 +x +12x +4=3x^2 +x
or,12x=-4
or,x=-4/12
or,x=-1/3

So the Correct answer is D
Intern  Joined: 08 Jan 2016
Posts: 3
If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?  [#permalink]

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Hi, Bunuel!
I solved this problem differently, but not sure if it's mathematically right:
(x + 4)(3x + 1) = 3x^2+ x
(x+4)(3x + 1)=x(3x+1)
(x+4)(3x+1)-x(3x+1)=0
(x+4-x)(3x+1)=0
so, first bracket is invalid, but second 3x=-1 gives the right answer x=-1/3.
What do you think CEO  G
Joined: 20 Mar 2014
Posts: 2531
Concentration: Finance, Strategy
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Re: If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?  [#permalink]

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I5O wrote:
Hi, Bunuel!
I solved this problem differently, but not sure if it's mathematically right:
(x + 4)(3x + 1) = 3x^2+ x
(x+4)(3x + 1)=x(3x+1)
(x+4)(3x+1)-x(3x+1)=0
(x+4-x)(3x+1)=0
so, first bracket is invalid, but second 3x=-1 gives the right answer x=-1/3.
What do you think This is correct. There is no such thing as "so, first bracket is invalid".

Once you get (x+4-x)(3x+1)=0 ---> (4)(3x+1)=0 ---> means that the product of 4 and 3x+1 is =0 ---> This can only happen if either one of them or both of them are zero.

Both can not be zero as one of it is already 4. Thus, it must be then that (3x+1)=0 ---> x=-1/3

Hope this helps.
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Senior Manager  G
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Posts: 467
Location: United States (LA)
If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?  [#permalink]

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$$(x+4)(3x+1)=3x^2+x$$
simplifying the given expression
$$3x^2+13x+4=3x^2+x$$
12x=-4
x=$$\frac{-1}{3}$$
Senior Manager  G
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Posts: 406
Location: India
GPA: 4
WE: Engineering (Energy and Utilities)
Re: If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?  [#permalink]

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If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?

(x + 4)(3x + 1) = 3x^2 + x
or,3x^2 +x +12x +4=3x^2 +x
or,12x=-4
or,x=-4/12
or,x=-1/3 Re: If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?   [#permalink] 16 Apr 2020, 09:42

# If (x + 4)(3x + 1) = 3x^2 + x, what is a possible value of x?  