Let f0, f1, f2, ..., fn, ... denote the Fibonacci sequence. By evaluating each of the following expressions for small values of n, conjecture a general formula and then prove it, using mathematical induction and the Fibonacci recurrence:
(a) f1 + f3 + ... + f2n-1
(b) f0 + f2 + ... + f2n
(c) f0 - f1 + f2 - ... + (-1)^n fn
(d) f0^2 + f1^2 + ... + fn^2