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# (2+√7)=?

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Senior Manager
Joined: 21 Oct 2013
Posts: 416

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29 Jun 2014, 13:00
3
8
00:00

Difficulty:

25% (medium)

Question Stats:

74% (01:25) correct 26% (01:50) wrong based on 252 sessions

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(2+√7)=?

A) 3/5
B) √3/(√7+2)
C) 3/(√7+2)
D) √3/(√7−2)
E) 3/(√7 − 2)
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Joined: 13 Jun 2013
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29 Jun 2014, 13:07
1
2
goodyear2013 wrote:
(2+√7)=?

A) 3/5
B) √3/(√7+2)
C) 3/(√7+2)
D) √3/(√7−2)
E) 3/(√7 − 2)

multiply numerator and denominator with √7-2, we will get

= (√7+2)(√7-2)/(√7-2)
=(√7)^2-(2)^2/ √7-2
=7-4/(√7-2)
=3/(√7-2)

hence E
Math Expert
Joined: 02 Sep 2009
Posts: 53792

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29 Jun 2014, 13:09
2
goodyear2013 wrote:
(2+√7)=?

A) 3/5
B) √3/(√7+2)
C) 3/(√7+2)
D) √3/(√7−2)
E) 3/(√7 − 2)

Multiply by $$\frac{2-\sqrt{7}}{2-\sqrt{7}}$$:

$$2+\sqrt{7}*\frac{2-\sqrt{7}}{2-\sqrt{7}}=\frac{4-7}{2-\sqrt{7}}=\frac{-3}{2-\sqrt{7}}=\frac{3}{\sqrt{7}-2}$$.

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Hope it helps.
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08 Aug 2017, 20:07
1
We know that (2+√7)=(√7 + 2)

In order to find the value of the expression,
we multiply and divide by the same number.
$$\frac{(√7 + 2)((√7 - 2)}{(√7 - 2)}$$
Simplifying the numerator we get (√7)^2 - (2)^2 = 7 - 4 = 3

Therefore, the value of the expression is $$\frac{3}{(√7 - 2)}$$ (Option E)
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29 Sep 2017, 02:03
I find it hard to grasp why a GMAT question would have a radical in the denominator for answers......? I believe from all the resources I have encountered with, there should not be a radical in the answer.........
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10 Jan 2019, 03:44
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: (2+√7)=?   [#permalink] 10 Jan 2019, 03:44
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