if f(1)=3 and f(n)=-2f(n-1), then f(5)=
\(f(n)=-2 f_{n-1} \\ f_{1} =3 \\ f(2)=-2 f_{1}=-2*(3)=-6 \\ f(3)=-2 f_{2}=-2*(-6)=12 \\ f(4)=-2 f_{3}=-2*(12)=-24 \\ f(5)=-2 f_{4}=-2*(-24)=48\)and\(f_{n} =3* (-2)^{n-1}\)