Answer
$\dfrac{2x}{7\sqrt{x}}$
Work Step by Step
Rationalizing the numerator of $
\dfrac{\sqrt{4x}}{7}
$ results to
\begin{array}{l}
\dfrac{2\sqrt{x}}{7}
\\\\=
\dfrac{2\sqrt{x}}{7}
\cdot
\dfrac{\sqrt{x}}{\sqrt{x}}
\\\\=
\dfrac{2\sqrt{x^2}}{7\sqrt{x}}
\\\\=
\dfrac{2x}{7\sqrt{x}}
.\end{array}