The square root of a number is only defined for non-negative numbers, since the square root of a negative number is not a real number.
For the expression sqaure root of -(6-x) to make sense mathematically, the expression inside the square root must be non-negative.
So, we need to find the values of x that make -(6-x) non-negative.
-(6-x) is non-negative when -(6-x) ≥ 0
Simplifying this inequality, we get 6-x ≤ 0
x ≤ 6
So, for x ≤ 6, the expression sqaure root of -(6-x) is defined and makes sense mathematically. This is the domain of the expression.
In summary, the domain of the expression sqaure root of -(6-x) is x ≤ 6.