81(x+y)平方-121(m+n)平方

分类: 作业答案 • 2022-03-25 13:38:38

问题描述：

答

原式=[9(x+y)]²-[11(m+n)]²
=(9x+9y)²-(11m+11n)²
=[(9x+9y)+(11m+11n)][(9x+9y)-(11m+11n)]
=(9x+9y+11m+11n)(9x+9y-11m-11n)