The differential equation of the family of circles passing through the origin and having centre at the line \( y = x \) is:
\( (x^{2}-y^{2}+2xy)\,dx = (x^{2}-y^{2}-2xy)\,dy \)
\( (x^{2}+y^{2}-2xy)\,dx = (x^{2}+y^{2}+2xy)\,dy \)
\( (x^{2}-y^{2}+2xy)\,dx = (x^{2}-y^{2}+2xy)\,dy \)
\( (x^{2}+y^{2}+2xy)\,dx = (x^{2}+y^{2}-2xy)\,dy \)