Answer
$\dfrac{\sqrt{7}}{7}$
Work Step by Step
RECALL:
for any nonnegative real number $a$, $\sqrt{a} \cdot \sqrt{a} = a.$
Rationalize the denominator by multiplying $\sqrt{7}$ to the numerator and the denominator, then use the rule above to obtain
$\dfrac{1}{\sqrt{7}} \cdot \dfrac{\sqrt{7}}{\sqrt{7}}
\\=\dfrac{\sqrt{7}}{7}.$
