Answer
$\sqrt2$
Work Step by Step
Rationalize the denominator by multiplying $\sqrt{2}$ to both the numerator and the denominator to have:
$=\dfrac{4}{\sqrt{8}} \cdot \dfrac{\sqrt{2}}{\sqrt{2}}
\\=\dfrac{4\sqrt{2}}{\sqrt{16}}
\\=\dfrac{4\sqrt2}{4}$
Cancel the common factor $4$ to have:
$=\sqrt2$
