jika f(x) = 2x + 3 dan g(x) = 9 - x , nilai dari (fog)^-1(-9) =

jawab

f(x) = 2x + 3
g(x)= 9 - x

fog(x)= f { g(x)} 
(fog)(x) = f (9 -x)
(fog)(x) =  2 (9-x) + 3
(fog)(x) = 18 - 2x + 3
(fog)(x) = 21 - 2x

(fog)⁻¹ (21 - 2x) = x
21 - 2x = -9
-2x = - 30
x = 15

(fog)⁻¹(-9) = 15