Soal no 70 umptn/B/1999

f(x) = 2x - 3, g(x) = 1/(3x + 1)
(f o g)(x) = f(g(x))
= 2g(x) - 3
= 2(1/(3x + 1)) - 3
= (2 - 3(3x + 1))/(3x + 1)
= (2 - 9x - 3)/(3x + 1)
= (-9x - 1)/(3x + 1) ====> -9 dan 1 ditukar posisi dan berubah tanda
(f o g)^-1(x) = (-x - 1)/(3x + 9) = - (x + 1)/(3x + 9)