The functions $f$ and $g$ are defined as follows. \[ f(x)=-4 x^{2}-3 \quad g(x)=2 x+4 \] Find $f(3)$ and $g(-6)$. Simplify your answers as much as possible. \[ f(3)= \] \[ g(-6)= \]

Step 1 ：The functions $f$ and $g$ are defined as follows. \[f(x)=-4 x^{2}-3 \] \[g(x)=2 x+4\]

Step 2 ：Find $f(3)$ and $g(-6)$. Simplify your answers as much as possible.

Step 3 ：To find $f(3)$, we need to substitute $x=3$ into the function $f(x)=-4x^2-3$. Similarly, to find $g(-6)$, we need to substitute $x=-6$ into the function $g(x)=2x+4$.

Step 4 ：Substituting $x=3$ into $f(x)$, we get $f(3)=-4(3)^2-3=-39$.

Step 5 ：Substituting $x=-6$ into $g(x)$, we get $g(-6)=2(-6)+4=-8$.

Step 6 ：Final Answer: \[f(3)=\boxed{-39}\] \[g(-6)=\boxed{-8}\]