Answer
$x=4 m$
Work Step by Step
For a fraction to equal zero, the numerator must equal zero. So, we solve
$$
\begin{aligned}
x^2-5 m x+4 m^2&= 0\\
(x-m)(x-4 m)& =0 \\
\end{aligned}
$$
This gives $x=4 m$ and when $x=m$. But $x=m$, the denominator will equal zero as well, so we must omit $x=m$.
The only solution is $x=4 m$.
