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by cans » Wed Sep 21, 2011 6:15 pm
√(9+√80)=A and √(9-√80)=B
thus (a+b)^2 = a^2 + b^2 + 2ab
a^2 = (9+√80)
b^2 = (9-√80)
ab=√(9+√80)√(9-√80) =√[(9+√80)(9-√80)]
(x+y)(x-y) = x^2 - y^2
thus ab = √(9^2 - (√80)^2) = 1
2ab=2
thus final ans = (9+√80) + (9-√80) + 2 = 20
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