x^2-7xy+6y^2m^2-2mn-15n^25x^2+6x-8

x^2-7xy+6y^2m^2-2mn-15n^25x^2+6x-8
x^2-7xy+6y^2
m^2-2mn-15n^2
5x^2+6x-8

x^2-7xy+6y^2m^2-2mn-15n^25x^2+6x-8
(x-6y)(x-y)
(m-5n)(m+3n)
(5x-4)(x+2)

(x-y)(x-6y)
(m+3n)(m-5n)
(5x-4)(x+2)

其实十字相乘只要把常数项拆为两个数的积,而这两个相加要等于一次项系数,就这么简单,自己试试吧~祝你好运~