Imagine a recursive f(x) defined as:
f(x) = f(-x) if x < 0
= 4*f(x-1) + 3 if x > 1
= 12 if x = 1
= 5 if x = 0
Implement f(x), assuming that the
parameter and the result are both integer. Write a driver for it that test
it with both positive and negative values (at least 4 cases).