If $ X + \frac{1}{2x}= 3,$ then evaluate

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Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:

If $ X + \frac{1}{2x}= 3,$ then evaluate $8x^3 +\frac{1}{x^3}$.

Options:

212

216

180

196

Correct Answer:

180

Explanation:

If $ X + \frac{1}{2x}= 3,$

Then, $8x^3 +\frac{1}{x^3}$ = ?

Multiply the equation with 2 = 2 ($ X + \frac{1}{2x}= 3,$)

=$ 2X + \frac{1}{x}= 6,$

$8x^3 +\frac{1}{x^3}$ = 6³ - 3 × 6 × 2 = 180