(x+y)(x-y)-y^2+(x-y)^2-(6x^2 y-2xy^2)÷2y
=x^2-y^2-y^2+x^2-2xy+y^2-(3x^2-xy)
=-(x^2+y^2+xy)
=-(x-y)^2-3xy
=-9+6
=-3
(x+y)(x-y)-y^2+(x-y)^2-(竖迟坦旦轿6x^2 y-2xy^2)÷2y
=x^2-y^2-y^2+x^2-2xy+y^2-2y(3x^2 -xy)÷2y
=2x^2-y^2-2xy-(余桐3x^2 -xy)
=-x^2-y^2-xy
=-(x-y)^2-2xy-xy
=-(x-y)^2-3xy
=-3^2-3*(-2)
-3