If ( x² + 1/(49x²) ) = 155/7 , then what is the value of (x + 1/7 x)?

If ( x² + 1/(49x²) ) = 155/7 , then what is the value of…

If $\left( {{x^2} + \frac{1}{{49{x^2}}}} \right) = 15\frac{5}{7}$ , then what is the value of (x + $\frac{1}{7}$ x)?

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Correct answer: D

Explanation

The correct answer is option 4 i.e. ±4.

$\left( {{x^2} + \frac{1}{{49{x^2}}}} \right) = 15\frac{5}{7}$

⇒ x² + $\frac{1}{49}$ x² + $\frac{2}{7}$ = $\frac{110}{7}$ + $\frac{2}{7}$

⇒ (x + $\frac{1}{7}$ x)² = 16

⇒ (x + $\frac{1}{7}$ x) = ± 4

Required answer is ± 4