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If (6 + 2/x)(x - 4) = 0, and x does not equal 4, then x =

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If (6 + 2/x)(x - 4) = 0, and x does not equal 4, then x =  [#permalink]

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New post 19 Oct 2017, 23:13
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A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

93% (01:07) correct 7% (02:09) wrong based on 91 sessions

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If (6 + 2/x)(x - 4) = 0, and x does not equal 4, then x =  [#permalink]

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New post 20 Oct 2017, 00:03
Bunuel wrote:
If \((6 + \frac{2}{x})(x - 4) = 0\), and x does not equal 4, then x =

(A) -6
(B) -4
(C) -1/3
(D) 1/3
(E) 3


\((6 + \frac{2}{x})(x - 4) = 0\)

\(6x - \frac{8}{x} - 24 + 2 = 0\)

\(6x - \frac{8}{x} - 22 = 0\)

\(6x^2 - 22x - 8 = 0\)

\(6x^2 - 24x + 2x - 8 = 0\) => \(6x(x - 4) + 2(x - 4) = 0\) => \((6x+2)(x-4) = 0 => x=4\) or \(-\frac{1}{3}\)

Since x cannot be 4, the other value of x = \(-\frac{1}{3}\)(Option C)
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Re: If (6 + 2/x)(x - 4) = 0, and x does not equal 4, then x =  [#permalink]

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New post 20 Oct 2017, 03:37
(6+\(\frac{2}{x}\))(x-4)=0
\(\frac{(6x+2)}{x}\) * (x-4)=0
(6x+2) * (x-4)=0 ---Cross multiplying by x
Therefore, x = \(\frac{-2}{6}\) = \(\frac{-1}{3}\) or 4
Since x is not equal to 4, x = \(\frac{-1}{3}\)
answer C.
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If (6 + 2/x)(x - 4) = 0, and x does not equal 4, then x =  [#permalink]

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New post 20 Oct 2017, 06:37
Bunuel wrote:
If \((6 + \frac{2}{x})(x - 4) = 0\), and x does not equal 4, then x =

(A) -6
(B) -4
(C) -1/3
(D) 1/3
(E) 3

You do not have to do much math here. Set the first term equal to 0 and you have your answer.

By the zero product rule, if
a * b = 0, then a = 0, or b = 0, or both = 0

x does not equal 4. Hence
(x - 4) cannot = 0. Therefore:

The first term, \((6 + \frac{2}{x})\) must equal 0.

(Plain English: you cannot have a product of 0 unless one or both of the factors is 0.)

\((6 + \frac{2}{x}) = 0\)

\(6 = - \frac{2}{x}\)

\(6x = - 2\)

\(x = -\frac{2}{6} = -\frac{1}{3}\)

Answer C
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Re: If (6 + 2/x)(x - 4) = 0, and x does not equal 4, then x =  [#permalink]

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New post 20 Oct 2017, 08:34
If x cannot be 4, (6+2/x) must be equal 0 to multiply (x-4) and obtain zero.

6+ 2/x = 0
2/x = -6
x = - 1 / 3
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Re: If (6 + 2/x)(x - 4) = 0, and x does not equal 4, then x =  [#permalink]

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New post 24 Oct 2017, 05:16
Bunuel wrote:
If \((6 + \frac{2}{x})(x - 4) = 0\), and x does not equal 4, then x =

(A) -6
(B) -4
(C) -1/3
(D) 1/3
(E) 3


Since x ≠ 4, we see that x - 4 can’t be 0, and therefore, in order for the product to equal 0, 6 + 2/x must equal 0:

6 + 2/x = 0

2/x = -6

2 = -6x

-1/3 = x

Answer: C
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Re: If (6 + 2/x)(x - 4) = 0, and x does not equal 4, then x =  [#permalink]

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New post 27 Oct 2017, 08:13
1
I got C, but I was an idiot of massive proportions and totally missed the shortcut. The hint is that (x-4) will not give you zero. Hence, you only need to solve for (6+[2][/x])=0.

I am guessing this cost me about 50 seconds and unneeded stress.
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Re: If (6 + 2/x)(x - 4) = 0, and x does not equal 4, then x = &nbs [#permalink] 27 Oct 2017, 08:13
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