Fungsi f dirumuskan f(x) = 4x+9, f(-1) = a dan f(b) = -3. Nilai dari a + b adalah...

f(x) = 4x + 9

Maka
f(-1) = a
f(-1) = 4(-1) + 9
f(-1) = -4 + 9
f(-1) = 5

a = 5

Nilai b :
f(b) = - 3
-3 = 4x + 9
-3 - 9 = 4x
-12 = 4x
-12/4 = x
-3 = x

Jadi nilai b = -3

Maka:
a + b = 5 + (-3) = 5 - 3 = 2