Question 448637
the "domain" specifies all the values that x can take for the given function:
-5 times the square root of x 
or
{{{f(x) = -5*sqrt(x)}}}
In this case, you just don't want the value under the radical to be negative (otherwise the result is an imaginary number).
So, the domain is
all real numbers equal to or greater than zero
OR
[0, +oo)
where
+oo is positive infinity