bagaimana cara megerjakan ini ???

(FoG) (x)=4x²-16x+19
F(g(x)) =4x²-16x+19
F( x-2) =4x²-16x+19
misal
x-2= a
x=a+2

4(a+2)²-16(a+2)+19
= 4(a²+4a+4)-16a-32+19
=4a²+8a+8-16a-32+19
=4a²-8a-5