Question : If $x=a+\frac{1}{a}$ and $y=a-\frac{1}{a}$, then the value of $x^4+y^4-2x^2y^2$ is:
Option 1: 4
Option 2: 8
Option 3: 16
Option 4: 64
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Correct Answer: 16
Solution : Given: $x=a+\frac{1}{a}$, $y=a-\frac{1}{a}$ Now, $x^2=(a+\frac{1}{a})^2=a^2+\frac{1}{a^2}+2$ And $y^2=(a-\frac{1}{a})^2=a^2+\frac{1}{a^2}-2$ Now, we know, $x^4+y^4-2x^2y^2=(x^2-y^2)^2$ $⇒x^4+y^4-2x^2y^2= [(a^2+\frac{1}{a^2}+2)-(a^2+\frac{1}{a^2}-2)]^2$ $\therefore x^4+y^4-2x^2y^2=(2+2)^2=16$ Hence, the correct answer is 16.
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Question : If $(x-\frac{1}{3})^2+(y-4)^2=0$, then what is the value of $\frac{y+x}{y-x}$?
Option 1: $\frac{11}{13}$
Option 2: $\frac{13}{11}$
Option 3: $\frac{16}{9}$
Option 4: $\frac{9}{16}$
Question : If $2x-\frac{2}{x}=1(x \neq 0)$, then the the value of $(x^3-\frac{1}{x^3})$ is:
Option 1: $\frac{13}{4}$
Option 2: $\frac{13}{8}$
Option 3: $\frac {17}{4}$
Option 4: $\frac{17}{8}$
Question : If $2x+\frac{2}{x}=3$, then the value of $x^{3}+\frac{1}{x^{3}}+2$ is:
Option 1: $\frac{3}{4}$
Option 2: $\frac{4}{5}$
Option 3: $\frac{5}{8}$
Option 4: $\frac{7}{8}$
Question : When $2x+\frac{2}{x}=3$, then the value of ($x^3+\frac{1}{x^3}+2)$ is:
Option 1: $\frac{2}{7}$
Option 2: $\frac{7}{8}$
Option 3: $\frac{7}{2}$
Option 4: $\frac{8}{7}$
Question : If $x=a^{\frac{1}{2}}+a^{-\frac{1}{2}}$, $y=a^{\frac{1}{2}}- a^{-\frac{1}{2}}$, then the value of $(x^{4}-x^{2}y^{2}-1)+(y^{4}-x^{2}y^{2}+1)$ is:
Option 1: 16
Option 2: 13
Option 3: 12
Option 4: 14
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