Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:

If x + \(\frac{1}{x}\) = 4

Find x5 + \(\frac{1}{x^5}\)

Options:

736

776

702

724

Correct Answer:

724

Explanation:

Formula → [x5 + \(\frac{1}{x^5}\) = (x3 + \(\frac{1}{x^3}\)) (x2 + \(\frac{1}{x^2}\)) - (x + \(\frac{1}{x}\))]

            → [x2 + \(\frac{1}{x^2}\) = a2 - 2 If x + \(\frac{1}{x}\) = a]

            → [x3 + \(\frac{1}{x^3}\) = a3 - 3a]

x + \(\frac{1}{x}\) = 4

x2 + \(\frac{1}{x^2}\) = 42 - 2 = 14

x3 + \(\frac{1}{x^3}\) = (4)3 - 3 × 4 = 52

Now; x5 + \(\frac{1}{x^5}\) = 52 × 14 - 4 = 724