若x+y=9,xy=20则 x^2+y^2=_, (x-y)^2=_

分类: 作业答案 • 2022-05-28 11:45:29

问题描述：

若x+y=9,xy=20则 x^2+y^2=_____, (x-y)^2=_____

答

x²+y²
=(x+y)²-2xy
=81-40
=41
(x-y)²
=x²+y²-2xy
=41-40
=1

若x+y=9,xy=20则 x^2+y^2=_____, (x-y)^2=_____