Patrick B. answered 07/14/19
Math and computer tutor/teacher
(1) Function and it's inverse are symmetric about the line y=x
(2)
f(f(x)) = (x+1)+1 = x+2
f_3(x) = (x+1)+2 = x+3
f_4(x) = (x+1)+3 = x+4
...
by induction... suppose f_n(x) = x+n
f_(n+1) = (x+1)+n = x+(n+1)
vs
f_2 comp f = (x+1)+2 = x+3
f_3 comp f = (x+3)+1 = x+4
....
again by induction...
if f_n = x+n then f_n comp f = (x+1)+n = x+(n+1)
therefore f_n comp f = f comp f_n = f_(n+1) = x +(n+1)
because
f comp f_n =
(x+n)+1 = x+(n+1) <--- associative
= x+(1+n) <--- commutative
= (x+1)+n <--- associative
= f_n comp f