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(8^(1/2) - 1))(1 - 8^(1/2))

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(8^(1/2) - 1))(1 - 8^(1/2))  [#permalink]

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New post 25 Jul 2018, 22:18
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A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

88% (00:59) correct 12% (01:20) wrong based on 46 sessions

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(8^(1/2) - 1))(1 - 8^(1/2))  [#permalink]

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New post 25 Jul 2018, 22:24
1
\((\sqrt{8} - 1)(1 - \sqrt{8})\)

=> \(\sqrt{8} - 8 -1 + \sqrt{8}\)

=> \(2\sqrt{8} - 9\)

=> \(4\sqrt{2} - 9\)

Hence option C
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Re: (8^(1/2) - 1))(1 - 8^(1/2))  [#permalink]

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New post 26 Jul 2018, 10:29
Bunuel wrote:
\((\sqrt{8} - 1)(1 - \sqrt{8})\)


A. \(2\sqrt{2} - 9\)

B. \(2\sqrt{2} - 8\)

C. \(4\sqrt{2} - 9\)

D. \(2\sqrt{2}\)

E. \(4\sqrt{2}\)


\((\sqrt{8} - 1)(1 - \sqrt{8})\)

= \(\sqrt{8}(1 - \sqrt{8})- 1(1 - \sqrt{8})\)

= \(\sqrt{8} - 8 - 1 + \sqrt{8}\)

= \(2\sqrt{8} - 9\)

= \(2\sqrt{2^3} - 9\)

= \(4\sqrt{2} - 9\), Answer must be (C)
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Re: (8^(1/2) - 1))(1 - 8^(1/2))  [#permalink]

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New post 30 Jul 2018, 10:32
Bunuel wrote:
\((\sqrt{8} - 1)(1 - \sqrt{8})\)


A. \(2\sqrt{2} - 9\)

B. \(2\sqrt{2} - 8\)

C. \(4\sqrt{2} - 9\)

D. \(2\sqrt{2}\)

E. \(4\sqrt{2}\)


FOILing, we have:

√8 - 8 - 1 + √8 = 2√8 - 9 = 2√4 x √2 - 9 = 4√2 - 9

Answer: C
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Re: (8^(1/2) - 1))(1 - 8^(1/2))   [#permalink] 30 Jul 2018, 10:32

(8^(1/2) - 1))(1 - 8^(1/2))

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