Question : If $2x=\sqrt{a}+\frac{1}{\sqrt{a}}, a>0$, then the value of $\frac{\sqrt{x^{2}-1}}{x-\sqrt{x^{2}-1}}$ is:
Option 1: $a+1$
Option 2: $\frac{1}{2}(a+1)$
Option 3: $\frac{1}{2}(a–1)$
Option 4: $a–1$
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Correct Answer: $\frac{1}{2}(a–1)$
Solution : Given: $2x=\sqrt{a}+\frac{1}{\sqrt{a}}, a>0$ $⇒2x=\sqrt{a}+\frac{1}{\sqrt{a}}$ $⇒x=\frac{1}{2}(\sqrt{a}+\frac{1}{\sqrt{a}})$ Calculating the value of ${\sqrt{x^{2}-1}}$ $⇒{\sqrt{x^{2}-1}}={\sqrt{(\frac{1}{2}(\sqrt{a}+\frac{1}{\sqrt{a}}))^{2}-1}}$ $⇒{\sqrt{(\frac{a^2-2a+1}{4a})}}=\frac{a-1}{2\sqrt{a}}$ So that $\frac{\sqrt{x^{2}-1}}{x-\sqrt{x^{2}-1}}$ becomes $⇒\frac{\sqrt{x^{2}-1}}{x-\sqrt{x^{2}-1}}=\frac{\frac{a-1}{2\sqrt{a}}}{\frac{1}{2}(\sqrt{a}+\frac{1}{\sqrt{a}})-(\frac{a-1}{2\sqrt{a}})}$ $⇒\frac{\sqrt{x^{2}-1}}{x-\sqrt{x^{2}-1}}=\frac{a-1}{2\sqrt{a}}×\frac{2\sqrt{a}}{2}=\frac{1}{2}(a–1)$ Hence, the correct answer is $\frac{1}{2}(a–1)$.
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Question : If $x$ = ${\frac{1}{\sqrt{2}+1}}$, then the value of $(x^{2}+2x–1)$ is:
Option 1: $\sqrt[2]{2}$
Option 2: 4
Option 3: 0
Option 4: 2
Question : If $x=\frac{1}{x-3},(x>0)$, then the value of $x+\frac{1}{x}$ is:
Option 1: $\sqrt{11}$
Option 2: $\sqrt{17}$
Option 3: $\sqrt{15}$
Option 4: $\sqrt{13}$
Question : If $x=\sqrt{–\sqrt{3}+\sqrt{3+8 \sqrt{7+4 \sqrt{3}}}}$ where $x > 0$, then the value of $x$ is equal to:
Option 1: 3
Option 3: 1
Question : If $x^4+\frac{16}{x^4}=15617, x>0$, then find the value of $x+\frac{2}{x}$.
Option 1: $\sqrt{121}$
Option 2: $\sqrt{129}$
Option 3: $\sqrt{123}$
Option 4: $\sqrt{127}$
Question : If $\frac{3}{(x+2)(2x+1)}=\frac{a}{2x+1}+\frac{b}{x+2}$ is an identity, the value of $b$ is:
Option 1: 0
Option 2: –1
Option 3: 2
Option 4: 3
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