GMAT Prep 2 - Square root and square

**Raam** · 10-13-2005, 03:37 AM

( sqrt( 9 + sqrt(80)) + sqrt( 9 - sqrt(80)) ) ^ 2 =

1. 1
2. 9-4sqrt(5)
3.18-4sqrt(5)
4.18
5.20

Please discuss. Thanks.

**chix475ntu** · 10-13-2005, 03:48 AM

(a+b)^2 = a^2+b^2 + 2ab
a^2 = 9+sqrt(80)
b^2 = 9-sqrt(80)
2ab = 2 * sqrt ([9+sqrt(80) * 9-sqrt(80)]) = 2 * 1 { (a+b) (a-b) = a^2 - b^2}

so 20

E

**Raam** · 10-13-2005, 04:05 AM

Oops ! How did I miss that??

Chix, thanks again.

**kronique** · 10-13-2005, 04:09 AM

ans. is E) 20...

**mydreamGMAT** · 10-13-2005, 05:55 AM

E it is

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