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# If (2x + 1)(x – 5) = 2 (x^2 – 1), what is the value of x

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If (2x + 1)(x – 5) = 2 (x^2 – 1), what is the value of x [#permalink]  06 Nov 2018, 16:15
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Question Stats:

82% (01:13) correct 17% (00:54) wrong based on 17 sessions

If $$(2x + 1)(x – 5) = 2 (x^2 – 1)$$, what is the value of x?

A. $$- \frac{1}{3}$$

B. $$- \frac{1}{5}$$

C. $$0$$

D. $$\frac{1}{3}$$

E. $$\frac{1}{2}$$
[Reveal] Spoiler: OA

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Re: If (2x + 1)(x – 5) = 2 (x^2 – 1), what is the value of x [#permalink]  08 Nov 2018, 03:23
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Carcass wrote:
If $$(2x + 1)(x – 5) = 2 (x^2 – 1)$$, what is the value of x?

A. $$- \frac{1}{3}$$

B. $$- \frac{1}{5}$$

C. $$0$$

D. $$\frac{1}{3}$$

E. $$\frac{1}{2}$$

Explanation::

$$(2x + 1)(x – 5) = 2 (x^2 – 1)$$

or $$2x^2 + x - 10x - 5= 2x^2 – 2$$

or $$-9x = 3$$

or $$x = -\frac{3}{9} = - \frac{1}{3}$$
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Re: If (2x + 1)(x – 5) = 2 (x^2 – 1), what is the value of x [#permalink]  13 Feb 2019, 13:37
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Expert's post
Carcass wrote:

If $$(2x + 1)(x – 5) = 2 (x^2 – 1)$$, what is the value of x?

A. $$- \frac{1}{3}$$

B. $$- \frac{1}{5}$$

C. $$0$$

D. $$\frac{1}{3}$$

E. $$\frac{1}{2}$$

pranab01's solution above is exactly how I'd solve the question.
However, if your algebra skills aren't that great, you can still solve the question by testing the answer choices

GIVEN EQUATION: (2x + 1)(x – 5) = 2 (x² – 1)

A) -1/3
Replace x with -1/3 to get: (2(-1/3) + 1)(-1/3 – 5) = 2((-1/3)² – 1)
Simplify: (-2/3 + 1)(-16/3) = 2(1/9 - 1)
Simplify more: (1/3)(-16/3) = 2(-8/9)
Evaluate: -16/9 = -16/9 PERFECT!!

Cheers,
Brent
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Brent Hanneson – Creator of greenlighttestprep.com

Re: If (2x + 1)(x – 5) = 2 (x^2 – 1), what is the value of x   [#permalink] 13 Feb 2019, 13:37
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