I have the problem:

Find the linear approximation about (-1,1) to the implicit function given by the relation: 2xy-x^{8}+y^{2}=-2

My problem is that trying implicit differentiation, I always get a slope which is not defined, because the denumerator is always (x+y) and therefore 0.

Did I do an error doing my calculation? If my calculation was right, can I answer that the tangent line is not defined at (-1,1)?