F(x) = 4x+3 ,jika f(2)= a dan f(b) =-9. Tentukan nilai a-b

F(2) = a
F(2) = 4(2) + 3
F(2) = 8 + 3 = 11

F(b) = F(x)
-9 = 4b + 3
-9 -3 = 4b
-12 = 4b
b = -12 : 4 = -3

a = 11 // b = -3
a-b = 11 - (-3) = 11 + 3 = 14