Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:

If $(x + \frac{1}{x})=\frac{11}{5}$, what is the value of $(x^3 + \frac{1}{x^3})$ ?

Options:

$4\frac{6}{125}$

$5\frac{101}{125}$

$10\frac{81}{125}$

$17\frac{31}{125}$

Correct Answer:

$4\frac{6}{125}$

Explanation:

We know that,

If x + \(\frac{1}{x}\)  = n

then, $x^3 +\frac{1}{x^3}$ = n3 - 3 × n

If $x + \frac{1}{x}=\frac{11}{5}$,

then, the value of $x^3 + \frac{1}{x^3}$ = ($\frac{11}{5}$)3 - 3 × $\frac{11}{5}$

= $\frac{1331}{125}$ - $\frac{33}{5}$

= $\frac{1331 - 825}{125}$

= $\frac{506}{125}$ = $4\frac{6}{125}$