Jika diketahui f(x)=x-3 , g(x)=5x+9 maka (g o f) invers x)=

gof(x)=g(f(x))= g(x-3)= 5(x-3)+9= 5x-6

y= 5x-6
y+6 =5x
x= (y+6)/5

jadi
invers gof(x)= (x+6)/5