用双十字相乘法先看x, x^2-x-6=(x-3)(x+2)再看y, -2y^2+7y-6=(3-2y)(y-2)最后看x、y, x^2-xy-2y^2=(x-2y)(x+y)x y -2 x -2y 3x^2-2y^2+xy-x+7y-6=(x+y-2)(x-2y+3)
