Question

x^2+y^2-2x+6y+10=0,求(x-y)^2-(x^2-y^2)

Answer 1

x^2+y^2-2x+6y+10

=(x-1)^2+(y+3)^2=0

x=1,y=-3

(x-y)^2-(x^2-y^2)

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

=(x-y)(x-y-x-y)

=(x-y)*(-2y)

=(1-(-3))*(-2*(-3))

=4*6

=24