Diketahui fungsi (f·g) (x) = 6x²-11x+15 , dan g (x) = 4x-3 . nilai fungsi f(5) adalah

mungkin yang di maksud soalnya begini ya?
(fog) (x) = 6x²-11x+15
jawab :
f(g(x)) = 6x²-11x+15
f(4x - 3) = 6x²-11x+15
misal p = 4x - 3
(p + 3)/4 = x
maka soal berubah menjadi
f(p) = 6((p + 3)/4)^2 - 11((p + 3)/4) + 15
f(p) = 6((p^2 + 6p + 9)/16) - 11p/4 - 33/4 + 15
f(p) = (6p^2)/16 + 36p/16 + 54/16 - 11p/4 - 33/4 + 15
f(p) = (6p^2)/16 + 36p/16 + 54/16 - 44p/16 - 132/16 + 240/16
f(p) = (6p^2)/16 - 8p/16 + 162/16
f(p) = (3p^2 - 4p + 81)/8
f(x) = (3x^2 - 4x + 81)/8
f(5) = (3(5)^2 - 4(5) + 81)/8
f(5) = (75 - 20 + 81)/8
f(5) = 17