diketahui f(x) = 2x²+x+3 dan g(x) = x+b. jika (fog)(0) = 9 dan b<0, nilai b adalah

jawab

f(x) = 2x² + x + 3
g(x) = ax + b

fog(0) = 9
f{g(0)} = 9
f (a(0)+b)) = 9
f(b) = 9
2b² + b + 3 = 9
2b² + b - 6 = 0
(2b - 3)(b  + 2)= 0
b = 3/2   atau b = - 2