Keerthana
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If N=(65)(6+5)mathrm{N}=frac{(sqrt{6}-sqrt{5})}{(sqrt{6}+sqrt{5})}, then what is the value of N+mathrm{N}+

(1N)?left(frac{1}{N} ight) ?

a

10

b

11

c

12

d

22

Answer : Option D
Explanation :

N=656+5=656+5×6565mathrm{N}=frac{sqrt{6}-sqrt{5}}{sqrt{6}+sqrt{5}}=frac{sqrt{6}-sqrt{5}}{sqrt{6}+sqrt{5}} imes frac{sqrt{6}-sqrt{5}}{sqrt{6}-sqrt{5}}

=(65)2(6)2(5)2=6+523065=frac{(sqrt{6}-sqrt{5})^{2}}{(sqrt{6})^{2}-(sqrt{5})^{2}}=frac{6+5-2 sqrt{30}}{6-5}

=11230=11-2 sqrt{30}

1 N=11+230 herefore frac{1}{mathrm{~N}}=11+2 sqrt{30}

N+1 N=11230+11+230=22 herefore mathrm{N}+frac{1}{mathrm{~N}}=11-2 sqrt{30}+11+2 sqrt{30}=22

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