Arturo O. answered 09/08/18
Tutor
5.0
(66)
Experienced Physics Teacher for Physics Tutoring
Try working with x = y = 0
f(0) = f(0 + 0) = f(0)f(0) ⇒
f(0) = f(0)2
f(0) = 0 or 1
If f(0) > 0, then f(0) = 1