Question : If $x^{4}+\frac{1}{x^{4}}=119$, then the values of $x^{3}+\frac{1}{x^{3}}$ are:
Option 1: $\pm 10\sqrt{13}$
Option 2: $\pm \sqrt{13}$
Option 3: $\pm 16\sqrt{13}$
Option 4: $\pm 13\sqrt{13}$
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Correct Answer: $\pm 10\sqrt{13}$
Solution : Given: $x^4+\frac{1}{x^4}=119$ Adding 2 on both sides, ⇒ $x^4+\frac{1}{x^4}+2=121$ ⇒ $(x^2+\frac{1}{x^2})^2=121$ ⇒ $(x^2+\frac{1}{x^2})=11,-11$ Since, $(x^2+\frac{1}{x^2})>0$, ⇒ $(x^2+\frac{1}{x^2})=11$ Adding 2 on both sides, ⇒ $x^2+\frac{1}{x^2}+2=13$ ⇒ $(x+\frac{1}{x})^2=13$ ⇒ $(x+\frac{1}{x})=\pm\sqrt{13}$ Cubing both sides, ⇒ $x^3+\frac{1}{x^3}+3(x)(\frac{1}{x})(x+\frac{1}{x})=\pm13\sqrt{13}$ ⇒ $x^3+\frac{1}{x^3}+3(\pm\sqrt{13})=\pm13\sqrt{13}$ ⇒ $x^3+\frac{1}{x^3}=\pm10\sqrt{13}$ Hence, the correct answer is $\pm10\sqrt{13}$.
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Question : If $x^2+\frac{1}{x^2}=29$, then find the value of $x-\frac{1}{x}$.
Option 1: $\pm 4$
Option 2: $\pm 3 \sqrt{3}$
Option 3: $\pm 3$
Option 4: $\pm 4 \sqrt{3}$
Question : If $x=\sqrt{3}-\frac{1}{\sqrt{3}}, y=\sqrt{3}+\frac{1}{\sqrt{3}}$, then the value of $\frac{x^2}{y}+\frac{y^2}{x}$ is:
Option 1: $\sqrt{3}$
Option 2: $3\sqrt{3}$
Option 3: $16\sqrt{3}$
Option 4: $2\sqrt{3}$
Question : If $x^{4}+\frac{1}{x^{4}}=16$, then what is the value of $x^{2}+\frac{1}{x^{2}}$?
Option 1: $3 \sqrt{2}$
Option 2: $2 \sqrt{2}$
Option 3: $5 \sqrt{2 }$
Option 4: $4 \sqrt{2}$
Question : If $x=(\sqrt{6}-1)^{\frac{1}{3}}$, then the value of $\left(x-\frac{1}{x}\right)^3+3\left(x-\frac{1}{x}\right)$ is:
Option 1: $\frac{2 \sqrt{6}-6}{5}$
Option 2: $\frac{4 \sqrt{6}-6}{5}$
Option 3: $\frac{4 \sqrt{6}-6}{3}$
Option 4: $\frac{4 \sqrt{3}-6}{5}$
Question : If $x=\frac{4\sqrt{15}}{\sqrt{5}+\sqrt{3}}$, the value of $\frac{x+\sqrt{20}}{x–\sqrt{20}}+\frac{x+\sqrt{12}}{x–\sqrt{12}}$ is:
Option 1: $1$
Option 2: $2$
Option 3: $\sqrt{3}$
Option 4: $\sqrt{5}$
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