Question : If $x^2-3x+1=0$, what is the value of $(x^4+\frac{1}{x^4})$?
Option 1: $11$
Option 2: $18$
Option 3: $47$
Option 4: $51$
Correct Answer: $47$
Solution : Given: $x^2-3x+1=0$ Divide both sides by $x$, we get, $⇒ x-3+\frac{1}{x}=0$ $\therefore x+\frac{1}{x}=3$ Squaring both sides, we get, $⇒(x+\frac{1}{x})^2=3^2$ $⇒x^2+\frac{1}{x^2}+2×x×\frac{1}{x}=9$ $\therefore x^2+\frac{1}{x^2}=7$ Again squaring both sides, we get, $⇒(x^2+\frac{1}{x^2})^2=7^2$ $⇒x^4+\frac{1}{x^4}+2×x^2×\frac{1}{x^2}=49$ $⇒(x^4+\frac{1}{x^4})=49-2$ $\therefore(x^4+\frac{1}{x^4})=47$ Hence, the correct answer is $47$.
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