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(1+5^1/2)(1-5^1/2)=

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(1+5^1/2)(1-5^1/2)=  [#permalink]

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New post 02 Jan 2014, 06:40
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A
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D
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The Official Guide For GMAT® Quantitative Review, 2ND Edition

\((1+\sqrt{5})(1-\sqrt{5})=\)

(A) -4
(B) 2
(C) 6
(D) \(-4-2\sqrt{5}\)
(E) \(6-2\sqrt{5}\)

Problem Solving
Question: 20
Category: Arithmetic Operations on radical expressions
Page: 64
Difficulty: 500


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Re: (1+5^1/2)(1-5^1/2)=  [#permalink]

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New post 02 Jan 2014, 06:54
1
Quite a simple question:(a+b)*(a-b)=a^2-b^2
So,(1+5^1/2)(1-5^1/2)=1-5=-4
Option A should be the answer.
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Re: (1+5^1/2)(1-5^1/2)=  [#permalink]

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New post 03 Jan 2014, 00:41
(1+\sqrt{5})(1-\sqrt{5})=

(A) -4
(B) 2
(C) 6
(D) -4-2\sqrt{5}
(E) 6-2\sqrt{5}

Sol: We know a^2-b^2= (a-b)(a+b).

Therefore the above can be re-written as (1^2-\sqrt{5}^2)------>(1-5)= -4 Ans A
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New post 05 Jan 2014, 11:18
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(1 + √5)(1 - √5)  [#permalink]

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New post 24 Aug 2016, 09:13
\((1 + \sqrt{5})(1 - \sqrt{5})\) =

a) \(-4\)
b) \(-2\)
c) \(6\)
d) \(-4 - 2\sqrt{5}\)
e) \(6 - 2\sqrt{5}\)
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New post 24 Aug 2016, 09:38
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New post 23 Oct 2019, 15:38
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: (1+5^1/2)(1-5^1/2)=   [#permalink] 23 Oct 2019, 15:38
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