Question

two interger a and b. f(x)=ax+b
f(f(0))=0 and
f(f(f(4)))=9

find f(f(f(f(10)))).

Answer 1

There is a similar problem around here. From the first part, you get that f(b) = 0 -> ab + b = 0, which implies that a = -1. So f(x) = -x + b. Expanding out the second part we get b = 13.
Now try out the last part :-)

Answer 2

Was this question on some kind of test earlier today? It was just asked right before your question.