Question

整体带入函数值,（急）已知x(x-1）-（x二次方-y)= --3,求x二次方+y二次方-2xy的值.

Answer 1

x(x-1)-(x²-y)=-3

x²-x-x²+y=-3

-x+y=-3

x-y=3

x²+y²-2xy

=(x-y)²

=3²

=9