Jika f (x) =ax+3 dan f (f (x)) =4x+9, maka nilai a^2+3a+3 adalah....

f(x) = ax + 3
f(f(x)) = 4x + 9
af(x) + 3 = 4x + 9
a(ax + 3) + 3 = 4x + 9
a^2 x + 3a + 3 = 4x + 9
Jadi
a^2 = 4 => a = 2

atau

3a + 3 = 9 => 3a = 6 => a = 2

Jadi
a^2 + 3a + 3 = 4 + 6 + 3 = 13