Answer
See the definition below.
Work Step by Step
To find the domain we will have to set the equation inside the square root greater than and equal to zero. Let us take an example:
$f(x)=\sqrt{5-x}$
Put the equation inside the square root greater than and equal to zero.
we have, $5-x \geq 0$
or $x \leq 5$
Thus, Domain will be: $(- \infty, 5]$
