Pakai jalannya Semoga dapat membantu

f(x) = 3x^ + x - 7
g(x) = 2x + 1
(fog)(x) = ?

fog (x) = f(g(x))
           = f(g(2x+1))
           = 3(2x+1)^ + 2x + 1 - 7
           = 3(2x + 1) (2x + 1) + 2x + 1 - 7
           = 3(4x^ + 2x + 2x + 1) + 2x + 1 - 7
           = 3(4x^ + 4x + 1) + 2x + 1 - 7
           = 12x^ + 12x + 3 + 2x + 1 - 7
           = 12x^ + 14x - 3 (D)