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Indices problem:Gmat prep-2

Expert replies
Source: — Problem Solving |

by kapsii » Sat Apr 04, 2009 10:23 pm
using (a+b)^2 = a^2 + b^2 + 2.a.b.

((9 +√80)^.5)^2 + ((9 -√80)^.5)^2 + 2.[{(9 +√80)^.5} * {(9 -√80)^.5}]

or 18 + 2 [((9 + √80)*(9 - √80))^0.5]

(a+b)(a-b) = a^2 - b^2

= 18 + 2* [(81-80)^0.5]
= 18 + 2
= 20.
Cheers,
Dubes
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by gmat740 » Sat Apr 04, 2009 11:52 pm
Thanks a lot

I made such a foolish mistake
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