Question

How do you find the domain for `g(x)=sqrt(40-8x)`?

Answer 1

Assuming we are restricted to Real values for
`g(x) = sqrt(40-8x)`
then
`g(x)` is defined for all Real values of `x` for which `(40-8x) >= 0`

That is for all Real values of `x<=5`

So the Domain of `g(x)` is `(-oo,+5]`