[(9+80^1/2)^1/2+(9-80^1/2)^1/2]^2
= [√(9 + 4√5) + √(9 - 4√5)]^2
It is of the form (a + b)^2 = a^2 + b^2 + 2ab
[√(9 + 4√5) + √(9 - 4√5)]^2 = 9 + 4√5 + 9 - 4√5 + 2√(9 + 4√5)√(9 - 4√5)
= 18 + 2√(81 - 80)
= 18 + 2 = 20
The correct answer is 20.
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[(9+80^1/2)^1/2+(9-80^1/2)^1/2]^2 ???
Source: Beat The GMAT — Problem Solving |
Rahul Lakhani
Quant Expert
Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)
Quant Expert
Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)
