tentukan rumus f(x) jika dik g(x)= 3x+1 dan (fog) (x)=4x-5

buat permisalan dulu:
3x + 1 = a
x = a - 1 / 3
( fog ) ( x ) = 4x - 5
( f ( g ( x ))) = 4x - 5
( f ( 3x + 1 )) = 4x - 5
pakai permisalan diatas
( f ( a )) = 4 ( a - 1 / 3 ) - 5
( f ( a )) = 4a - 4 - 5 / 3
( f ( a )) = 4a - 9 / 3
( f ( a )) = 4a - 3
dapat disimpulkan:
f(x) = 4x - 3

semoga benar