x+y=4,xy=2则（x-y）²＝﹙ ﹚

来源：学生作业学帮网编辑：学帮网时间：2024/06/03 02:53:08

（x-y）²
＝x^2-2xy+y^2
=x^2+2xy+y^2-4xy
=(x+y)^2-4xy
=8

（x-y）²
=（x+y）² - 4xy
=16 - 8
=8

x+y=4,xy=2则（x-y）²＝8