Question

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

Answer 1

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^2-4x = 0`
or
`(x)(x-4) = 0`

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