Question : If $x+\frac{1}{x}=\mathrm{\frac{K}{2}}$, then what is the value of $\frac{x^8+1}{x^4} ?$
Option 1: $\frac{\mathrm{K}^4-16 \mathrm{~K}^2+32}{16}$
Option 2: $\frac{\mathrm{K}^4-8 \mathrm{~K}^2-36}{32}$
Option 3: $\frac{\mathrm{K}^4-8 \mathrm{~K}^2-32}{16}$
Option 4: $\frac{\mathrm{K}^4-8 \mathrm{~K}^2+32}{16}$
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Correct Answer: $\frac{\mathrm{K}^4-16 \mathrm{~K}^2+32}{16}$
Solution : $x + \frac{1}{x} = \frac{K}{2}$ $⇒\left(x + \frac{1}{x}\right)^2 = \mathrm{\left(\frac{K}{2}\right)^2}$ $⇒x^2 + 2 + \frac{1}{x^2} = \mathrm{\frac{K^2}{4}}$ $⇒x^2 + \frac{1}{x^2} =\mathrm{ \frac{K^2}{4} - 2}$ Now, square this equation: $⇒\left(x^2 + \frac{1}{x^2}\right)^2 = \mathrm{\left(\frac{K^2}{4} - 2\right)^2}$ $⇒x^4 + 2 + \frac{1}{x^4} = \mathrm{\left(\frac{K^2}{4} - 2\right)^2}$ $⇒x^4 + \frac{1}{x^4} = \mathrm{\left(\frac{K^2}{4} - 2\right)^2 - 2}$ $⇒\frac{x^8+1}{x^4} =\mathrm{(\frac{K^4}{16}-K^2+4)-2}$ $⇒\frac{x^8+1}{x^4} =\mathrm{(\frac{K^4}{16}-K^2+2)}$ $\therefore \frac{x^8+1}{x^4} =\mathrm{(\frac{K^4-16K^2+32}{16})}$ Hence, the correct answer is $\mathrm{(\frac{K^4-16K^2+32}{16})}$.
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Question : What is the value of $\left(\mathrm{k}+\frac{1}{\mathrm{k}}\right)\left(\mathrm{k}-\frac{1}{\mathrm{k}}\right)\left(\mathrm{k}^2+\frac{1}{\mathrm{k}^2}\right)\left(\mathrm{k}^4+\frac{1}{\mathrm{k}^4}\right)$?
Option 1: $\mathrm{k}^{16}+\frac{1}{\mathrm{k}^{16}}$
Option 2: $\mathrm{k}^{16}-\frac{1}{\mathrm{k}^{16}}$
Option 3: $\mathrm{k}^8-\frac{1}{\mathrm{k}^8}$
Option 4: $\mathrm{k}^8+\frac{1}{\mathrm{k}^8}$
Question : If $x+\frac{1}{x}=2 K$, then what is the value of $x^4+\frac{1}{x^4}$?
Option 1: $16 {K}^4-16 {K}^2-1$
Option 2: $8 {K}^4+4 {K}^2-1$
Option 3: $16 {K}^4-16 {K}^2+2$
Option 4: $16 {K}^4-4 {K}^2-1$
Question : If $\sqrt{\frac{\mathrm{a}}{\mathrm{b}}}=\frac{8}{3}-\sqrt{\frac{\mathrm{b}}{\mathrm{a}}}$ and $a-b=10$, then the value of $ab$ is:
Option 1: $32 \frac{1}{7}$
Option 2: $32 \frac{3}{7}$
Option 3: $32 \frac{4}{7}$
Option 4: $32 \frac{2}{7}$
Question : What is the value of $\left(k-\frac{1}{k}\right)\left(k^2+\frac{1}{k^2}\right)\left(k^4+\frac{1}{k^4}\right)\left(k^8+\frac{1}{k^8}\right)\left(k^{16}+\frac{1}{k^{16}}\right) ?$
Option 1: $k^{64}-\frac{1}{k^{64}}$
Option 2: $\frac{k^{32}-\frac{1}{k^{32}}}{k-\frac{1}{k}}$
Option 3: $k^{32}-\frac{1}{k^{32}}$
Option 4: $\frac{k^{32}-\frac{1}{k^{32}}}{k+\frac{1}{k}}$
Question : What is the value of $\frac{1+\mathrm{x}}{1-\mathrm{x}^2} \div \frac{1+\mathrm{x}}{1-\mathrm{x}^4}-\frac{1-\mathrm{x}^4}{1-\mathrm{x}} \times \frac{1+\mathrm{x}}{1-\mathrm{x}^2}$?
Option 1: $\frac{2 \mathrm{x}\left(1+\mathrm{x}^2\right)}{(1-\mathrm{x})}$
Option 2: $\frac{2 \mathrm{x}\left(1+\mathrm{x}^2\right)}{(\mathrm{x}-1)}$
Option 3: $(1-\mathrm{x})^2$
Option 4: $\left(1+\mathrm{x}^2\right)$
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