Answer
$\dfrac{\sqrt{10}}{5}$
Work Step by Step
RECALL:
for any nonnegative real number $a$, $\sqrt{a} \cdot \sqrt{a} = a.$
Rationalize the denominator by multiplying $\sqrt{10}$ to the numerator and the denominator, then use the rule above to obtain
$\dfrac{2}{\sqrt{10}} \cdot \dfrac{\sqrt{10}}{\sqrt{10}}
\\=\dfrac{2\sqrt{10}}{10}.$
Simplify by canceling the common factor to obtain
$\require{cancel}
\dfrac{\cancel{2}\sqrt{10}}{\cancel{2}(5)}
\\=\dfrac{\sqrt{10}}{5}.$
