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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 |
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