You can
put this solution on YOUR website!your equation is

A graph of this equation is shown below.

-----
at x = 3, (x-3) in the denominator causes a division by zero which causes the value to be undefined at that point.
-----
At x < 3, (x-3) causes the denominator to be negative which causes the expression within the square root sign to be negative which results in the function not having real values at that point.
-----
The domain of the function

is all value of x > 3.
The range of the function is all values of y > 0.
-----
y will never be equal to 0 no matter how large x gets because the numerator in the fraction underneath the square root sign is a constant. It will approach 0 but never touch it.
-----
The same graph but carrying x out a lot further shows this to be true.

-----
I didn't understand the second part of your question.
Maybe answering the first part helped you with the second part?
-----