Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:

If $x-\frac{1}{x}=1$, then what is the value of $x^8+\frac{1}{x^8} ?$

Options:

3

119

47

-1

Correct Answer:

47

Explanation:

If $K+\frac{1}{K}=n$

then, $K^2+\frac{1}{K^2}$ = n2 – 2

If $K-\frac{1}{K}=n$

then, $K^2+\frac{1}{K^2}$ = n2 + 2

If $x-\frac{1}{x}=1$

then, $x^2+\frac{1}{x^2}$ = 12 + 2 = 3

$x^4+\frac{1}{x^4}$ = 32 – 2 = 7

And the value of $x^8+\frac{1}{x^8} $ = 72 – 2  = 47