Summary: To do the reverse mathematical induction of N, first we get that when n = 2 k, k= 1, k+ 1, which are very simple to use A+B >; =√(ab) can be proved.

The key is the following reverse mathematical induction. If n holds for n- 1, then an=(n- 1) is multiplied by √(a 1a2...a(n- 1), and then it is substituted into the established formula of n, and after sorting, N-65448 can be obtained. ?

So it is proved that in n = 2 k, what is the value range of k, and k is a positive integer. The first step is to sum the k powers of 2, 4, 8, 16, 32 ... The general mathematical induction is to prove that when n is greater than n, it is also true, while the reverse mathematical induction is to compare numbers less than n on the premise that n is true.