You can put this solution on YOUR website! Squares need to be >=0. Thus
x-3>=0
Implies x must be >=3
We cannot divide by zero, thus 6-3x cannot =0.
Find where that is the case. 6=3x ->x=2
So we have x cannot be 2 and must be >=3.
We thus have the following domain in interval notation: [3,).
Since the numerator will always be positive or =0, we need only look at the denominator and see that this will always be negative (because x>=3 this means 6-3x<-3) except when x=3 (which gives y=0).
We thus have the follow range in interval notation: (,0]
I will plot the graph for you as a check:
(