Solution: Explain why Fermat's Last Theorem cannot be proved by mathematical induction.
This question is not easy to answer. The hypothesis can be proved by induction. First, for the case of a=2, if it can be proved that 2 (p- 1) = 1 (mod p), then induction is used again, that is, it holds for smaller p and for larger p, but there is no way to find the recurrence relation.