The range is the resulting y-values we get after substituting all the possible x-values.
[tex]\text{The domain:}\\\\-3\leq x < 0\to\{-3,\ -2,\ -1\}\\\\\text{The range:}[/tex]
Substitute the values of x to the equation of the function:
[tex]f(-3)=-(-3)^2=-9\\\\f(-2)=-(-2)^2=-4\\\\f(-1)=-(-1)^2=-1\\\\\boxed{\{-9,\ -4,\ -1\}}[/tex]
