# How do you find all numbers that must be excluded from the domain of the given rational expression 8/(x^2-4x)?

Apr 7, 2015

Division by $0$ is undefined
therefore we must exclude any values of $x$ which would cause the denominator to be $0$.

Those values would be given by
${x}^{2} - 4 x = 0$
or
$\left(x\right) \left(x - 4\right) = 0$

Therefore we must exclude
$x = 0$
and
$x = 4$
from the domain of this expression