a^5-a=a(a+1)(a-1)(aa+1)=a(a+1)(a-1)(aa-4+5)=a(a+1)(a-1)(aa-4)+5a(a+1)(a-1)=(a-2)(a-1)a(a+1)(a+2) + 5(a-1)a(a+1)已知连续5个数必有一个被5整除已知连续2个数必有一个被2整除已知连续3个数必有一个被3整除(2*3*...