1.

If x = √5 + 2, then the value of x – 1/x isA) 2√5 B) 4C) -4 D) -2√5

Answer»

Correct option is (B) 4

\(\because\) \(x=\sqrt{5}+2\)

\(\therefore\) \(\frac1x=\frac1{\sqrt{5}+2}\) \(=\frac{\sqrt{5}-2}{(\sqrt{5}+2)(\sqrt{5}-2)}\)

\(=\frac{\sqrt{5}-2}{5-4}\) \(=\sqrt{5}-2\)

\(\therefore\) \(x-\frac{1}{x}\) \(=(\sqrt{5}+2)-(\sqrt{5}-2)=4\)

Correct option is  A) 2√5



Discussion

No Comment Found