m是奇数，且m>=3
=>m可以用表达式2n-1，n>=2
=>m²-1 = (2n-1)²-1
=>m²-1 = 4n²-4n+1-1
=>m²-1 = 4n²-4n
=>m²-1 = 4n(n-1)
=>m²-1 = 4*奇数*偶数
由于n>=2，则4*奇数*偶数必然能被8整除
=>m²-1必然能被8整除
=>m(m²-1)必然也能被8整除