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# 8x^2 – 18 =

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Math Expert
Joined: 02 Sep 2009
Posts: 52392

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21 May 2017, 11:40
00:00

Difficulty:

15% (low)

Question Stats:

94% (00:36) correct 6% (01:13) wrong based on 23 sessions

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$$8x^2 – 18 =$$

(A) $$8(x^2 – 2)$$

(B) $$2(2x + 3)(2x – 3)$$

(C) $$2(4x + 3)(4x – 3)$$

(D) $$2(2x + 9)(2x – 9)$$

(E) $$2(4x + 3)(x – 3)$$

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Re: 8x^2 – 18 =  [#permalink]

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21 May 2017, 12:00
2(2x+3)(2x–3) = 2(4x^2 - 9 ) = 8x^2 - 18 .

Hence the answer is option B.
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Re: 8x^2 – 18 =  [#permalink]

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21 May 2017, 14:24
Bunuel wrote:
$$8x^2 – 18 =$$

(A) $$8(x^2 – 2)$$

(B) $$2(2x + 3)(2x – 3)$$

(C) $$2(4x + 3)(4x – 3)$$

(D) $$2(2x + 9)(2x – 9)$$

(E) $$2(4x + 3)(x – 3)$$

8$$x^2$$ - 18 =

Factor out a 2 to get 2 * (4$$x^2$$ - 9)

(4$$x^2$$ - 9) is difference of squares, where (a$$^2$$ - b$$^2$$) = (a + b)(a - b), hence

2*(2x + 3)(2x - 3) is

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Re: 8x^2 – 18 = &nbs [#permalink] 21 May 2017, 14:24
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