3*5*17*（2^8+1）
=3*5*17*（2^8+1）（2^8-1）*除以（2^8-1）
=3*5*17*（2^8+1）（2^8-1）*除以[(2^4-1)(2^4+1)]
=3*5*17*（2^8+1）（2^8-1）*除以[(2^2-1)(2^2+1)(2^4+1)]
=3*5*17*（2^8+1）（2^8-1）*除以[(2-1)(2+1)(2^2+1)(2^4+1)]
=3*5*17*（2^8+1）（2^8-1）*除以[1*3*5*17]
=（2^8+1）（2^8-1）
=2^16-1
=65535
40又2/3*39又1/3
=(40+2/3)(40-2/3)
=40^2-(2/3)^2
=1600-4/9
=1599又5/9