123456.6×123456.6-123456.5×123456.7简便计算

123456.6×123456.6-123456.5×123456.7=123456.6×123456.6-（123456.6-0.1）×（123456.6+0.1）=123456.6×123456.6-（123456.6×123456.6-0.1×0.1）=123456.6×123456.6-123456.6×123456.6+0.01=0.01