f(x)= x+3 dan (g o f) (x)=2x^2 + 13x + 16 maka g(3x)=....

g(f(x)) = 2x^2+13x+16
g(x+3) = 2x^2+13x+16

x+3=y => x=y-3

g(y) = 2(y-3)^2+ 13(y-3) + 16
g(y) = 2(y^2-6y+9) + 13(y-3) +16
g(y) = 2y^2-12y+18+13y-39+16
g(y) = 2y^2+y-5
g(x) = 2x^2+x-5
g(3x) = 2(3x)^2 +3x-5
g(3x) = 18x^2+3x-5