1 3
1 -1
x² +2xy-3y ²+3x+ y+ 2
=(x+3y)(x-y)+3x+y+2
x+3y 2
x-y 1
=(x+3y+2)(x-y+1)请重打一遍，没看懂，谢了。(x² +2xy-3y ²)+3x+ y+ 2
【十字相乘法】
13
1-1

=(x+3y)(x-y)+3x+y+2
【十字相乘法】
x+3y 2
x-y 1
=(x+3y+2)(x-y+1)