Have in mind that as you cannot take the square root of a negative number, this means that x-4 CANNOT be negative. So it's either 0 or it's positive.
So we proceed like this:x−4≥0
x−4+4≥0+4
x≥4
So the domain is {x|x≥4}
In interval notation, the domain is [4,∞)
I hope thi can help you
