Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:

If $x^4+\frac{1}{x^4}=727, x>1$, then what is the value of $\left(x-\frac{1}{x}\right)$ ?

Options:

6

-6

-5

5

Correct Answer:

5

Explanation:

If x4 + \(\frac{1}{x^4}\) = a

then x2 + \(\frac{1}{x^2}\) = \(\sqrt {a + 2}\) = b

and x - \(\frac{1}{x}\) = \(\sqrt {b - 2}\)

If $x^4+\frac{1}{x^4}=727, x>1$

then x2 + \(\frac{1}{x^2}\) = \(\sqrt {727 + 2}\) = 27

and x - \(\frac{1}{x}\) = \(\sqrt {27 - 2}\) = 5