Question : If $\left(x^2 - \frac{1}{x^2}\right) = 4 \sqrt{6}$ and $x>1$, what is the value of $\left(x^3 - \frac{1}{x^3}\right)?$
Option 1: $20 \sqrt{2}$
Option 2: $24 \sqrt{2}$
Option 3: $18 \sqrt{2}$
Option 4: $22 \sqrt{2}$
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Correct Answer: $22 \sqrt{2}$
Solution : Given: $x^2 -\frac{1}{x^2} = 4\sqrt6$ Squaring both sides we get, ⇒ $x^4 +\frac{1}{x^4} - 2 = 96$ ⇒ $x^4 +\frac{1}{x^4}+2 = 98+2$ ⇒ $ (x^2+\frac{1}{x^2})^2 =100$ ⇒ $x^2 +\frac{1}{x^2} = 10$ ---------------(1) ⇒ $x^2 +\frac{1}{x^2} -2= 10-2$ ⇒ $(x-\frac{1}{x})^2=8$ ⇒ $(x-\frac{1}{x}) = 2\sqrt2$ ----------------(2) So, $x^3 -\frac{1}{x^3} = (x-\frac{1}{x})(x^2 +\frac{1}{x^2}+ x×\frac{1}{x})$ ⇒ $x^3 -\frac{1}{x^3}= 2\sqrt2 × (10+1)= 22\sqrt2$ Hence, the correct answer is $22\sqrt2$.
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Question : If $\left(x+\frac{1}{x}\right)=2 \sqrt{2}$ and $x>1$, what is the value of $\left(x^6-\frac{1}{x^6}\right)$?
Question : If $\left(x+\frac{1}{x}\right)=\sqrt{6}$ and $x>1$, what is the value of $\left(x^8-\frac{1}{x^8}\right)$?
Question : If $(x+\frac{1}{x})=6$ and $x>1$, find the value of $(x^2–\frac{1}{x^2})$.
Question : If $\left(x-\frac{1}{x}\right)^2=12$, what is the value of $\left(x^2-\frac{1}{x^2}\right)$, given that $x>0$?
Question : If $\left(x^2+\frac{1}{x^2}\right)=6$ and $0<x<1$, what is the value of $x^4-\frac{1}{x^4}$?
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