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# Which of the following equals

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Which of the following equals [#permalink]  09 Aug 2017, 15:23
Expert's post
00:00

Difficulty:

5% (low)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

Which of the following equals - ( \sqrt{2} - \sqrt{8} ) ( 2 \sqrt{2} + \sqrt{8} ) ?

A. -8 \sqrt{2}

B. -4

C. 4

D. 4 \sqrt{2}

E. 8
[Reveal] Spoiler: OA

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Kudos [?]: 449 [1] , given: 3

Re: Which of the following equals [#permalink]  12 Aug 2017, 06:03
1
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Expert's post
Carcass wrote:
Which of the following equals - ( \sqrt{2} - \sqrt{8} ) ( 2 \sqrt{2} + \sqrt{8} ) ?

A. -8 \sqrt{2}

B. -4

C. 4

D. 4 \sqrt{2}

E. 8

Let's apply the FOIL method.

We'll also use the fact that (√a)(√b) = √(ab)

So, -(√2 - √8)(2√2 + √8) = -(2√4 + √16 - 2√16 - √64)
= -(4 + 4 - 8 - 8)
= -(-8)
= 8

[Reveal] Spoiler:
E

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Re: Which of the following equals   [#permalink] 12 Aug 2017, 06:03
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