MCQ
If $\text{x}=4-\sqrt{15},$ then the value of $(\text{x}+\frac{1}{\text{x}})$ is:
  • A
    $7$
  • B
    $10$
  • C
    $6$
  • $8$

Answer

Correct option: D.
$8$

$\text{x}+\frac{1}{\text{x}}=\frac{\text{x}^2+1}{\text{x}}$
Now, put, $\text{x}=4-\sqrt{15}$
$\Rightarrow\frac{(-4\sqrt{15})^2+1}{4-\sqrt{15}}$
$\Rightarrow\frac{16+15-8\sqrt{15}+1}{4-\sqrt{15}}$
$\Rightarrow\frac{32-8\sqrt{15}}{4-\sqrt{15}}$
$\Rightarrow8$

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