分解因式:2xy+9-x^2-y^2

分类: 作业答案 • 2022-01-09 18:04:15

问题描述：

分解因式:2xy+9-x^2-y^2

答

2xy+9-x^2-y^2
=9-x^2-y^2+2xy
=9-(x^2+y^2-2xy)
=9-(x-y)^2
=[3-(x-y)][3+(x-y)]
=(3-x+y)(3+x-y)