Question

已知x(x-1)-(x的二次方-y)=-2,求2/x的二次方+y的二次方-xy

Answer 1

x(x-1)-(x^2-y)=-2

x^2-x-x^2+y=-2

y-x=-2

x-y=2

(x^2+y^2)/2-xy

=(x^2+y^2-2xy)/2

=(x-y)^2/2

=2^2/2

=2