We have the following:
[tex]\begin{gathered} -a^2+c\cdot(a-c)-n^2 \\ a=-3 \\ c=-2 \\ n=3 \end{gathered}[/tex]Evaluate:
[tex]\begin{gathered} -(-3)^2+(-2)\cdot(-3-(-2))-3^2 \\ -9+(-2)\cdot(-1)-9 \\ -9+2-9=-18+2=-16 \end{gathered}[/tex]The answer is -16