Question : If $x^{2} -3x +1=0$, then the value of $\frac{\left(x^4+\frac{1}{x^2}\right)}{\left(x^2+5 x+1\right)}$ is:
Option 1: $\frac{9}{4}$
Option 2: $\frac{27}{8}$
Option 3: $\frac{5}{2}$
Option 4: $2$
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Correct Answer: $\frac{9}{4}$
Solution : Given: $x^{2} -3x +1=0$ $⇒x^{2} +1 = 3x$ Dividing $x$ on both sides, we get, $⇒x + \frac{1}{x} = 3$ Cubing both sides, we get, $⇒(x+\frac{1}{x})^3=3^3$ $⇒x^3+\frac{1}{x^3}+3×x×\frac{1}{x}(x+\frac{1}{x})=27$ $⇒x^3+\frac{1}{x^3}+3×3=27$ $⇒x^3+\frac{1}{x^3}=18$ Now, $ \frac{x^4 +\frac{1}{x^2}}{x^2 + 5x + 1}$ $= \frac{x(x^3 +\frac{1}{x^3})}{x(x + 5 + \frac{1}{x})}$ $= \frac{x^3 +\frac{1}{x^3}}{x + 5 + \frac{1}{x}}$ $= \frac{18}{3+5}$ $= \frac{18}{8}$ $= \frac{9}{4}$ Hence, the correct answer is $\frac{9}{4}$.
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Question : The value of $15 \div 8-\frac{5}{4}$ of $\left(\frac{8}{3} \times \frac{9}{16}\right)+\left(\frac{9}{8} \times \frac{3}{4}\right)-\left(\frac{5}{32} \div \frac{5}{7}\right)+\frac{3}{8}$ is:
Question : If $\frac{x}{2}-\frac{\left [4\left (\frac{15}{2}-\frac{x}{3} \right ) \right ]}{3} = –\frac{x}{18}$ then what is the value of $x$?
Question : If $x\left(3-\frac{2}{x}\right)=\frac{3}{x}$, then the value of $x^3-\frac{1}{x^3}$ is equal to:
Question : If $x+\left [\frac{1}{(x+7)}\right]=0$, what is the value of $x-\left [\frac{1}{(x+7)}\right]$?
Question : If $\frac {x^2+3x+1}{x^2–3x+1}=\frac{1}{2 }$, then the value of $(x+\frac{1}{x})$ is:
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