Functions Question 618
Question: If $ f(x)=\frac{1}{\sqrt{x+2\sqrt{2x-4}}}+\frac{1}{\sqrt{x-2\sqrt{2x-4}}} $ for $ x>2 $ , then $ f(11)= $
[EAMCET 2003]
Options:
A) 7/6
B) 5/6
C) 6/7
D) 5/7
Show Answer
Answer:
Correct Answer: C
Solution:
$ f(x)=\frac{1}{\sqrt{x+2\sqrt{2x-4}}}+\frac{1}{\sqrt{x-2\sqrt{2x-4}}} $ $ f(11)=\frac{1}{\sqrt{11+2\sqrt{18}}}+\frac{1}{\sqrt{11-2\sqrt{18}}} $ $ =\frac{1}{3+\sqrt{2}}+\frac{1}{3-\sqrt{2}}=\frac{3-\sqrt{2}}{7}+\frac{3+\sqrt{2}}{7}=\frac{6}{7} $ .
BETA
