Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:

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

then find the value of  x2 - \(\frac{1}{x^2}\).

Options:

2\(\sqrt{2}\)

3\(\sqrt{6}\)

4\(\sqrt{3}\)

4\(\sqrt{2}\)

Correct Answer:

4\(\sqrt{3}\)

Explanation:

⇒ If x - \(\frac{1}{x}\) = a then x + \(\frac{1}{x}\) = \(\sqrt {a^2 + 4}\)

Here,

x - \(\frac{1}{x}\) =2\(\sqrt{2}\), then 

⇒  x + \(\frac{1}{x}\) = \(\sqrt {(2\sqrt{2})^2 + 4}\) = 2\(\sqrt{3}\)

Formula → x2 - y2 = (x + y) (x - y)

⇒ x2 - \(\frac{1}{x^2}\) = (x + \(\frac{1}{x}\)) (x - \(\frac{1}{x}\))

                = 2\(\sqrt {3}\) × 2\(\sqrt{2}\)

                = 4\(\sqrt{6}\)