古剑奇谭之剑魔剑仙:因式分解

来源:百度文库 编辑:高考问答 时间:2024/04/30 12:24:47
已知x-y=1,求x^3-y^3-3xy-5的值

x^3-y^3-3xy-5 = (x-y)(x^2 + xy +y^2) -3xy - 5
= x^2 + xy +y^2 - 3xy - 5
= x^2 - 2xy +y^2 - 5
= (x - y)^2 - 5
= 1 - 5
= -4