We have:g(-3)=2.(-3)+4=-6+4=-2

\(\Rightarrow\)f(g(-3))=f(-2)=(-2)²-2=4-2=2

\(f\left(g\left(-3\right)\right)=f\left(-3\cdot2+4\right)=f\left(-2\right)=\left(-2\right)^2-2=2\)