已知x^2-xy=60,xy-y^2=40,求代数式x^2-y^2和x^-2xy+y^2的值快算式和答案_其他解答

已知x^2-xy=60,xy-y^2=40,求代数式x^2-y^2和x^-2xy+y^2的值
快算式和答案

人气：256 ℃　时间：2019-08-19 02:56:25

解答

x^2-xy=60,xy-y^2=40,
x^2-y^2
=(x^2-xy)+(xy-y^2)
=60+40
=100
x^2-2xy+y^2
=(x^2-xy)-(xy-y^2)
=60-40
=20