Differential Equations

$x^2+y^2=3 x y+y+C$

$(2 x-3 y)^2+(3 x+2 y)^2=C$

$x^2+y^2+3 x y-4 x-7 y+C=0$

$x^2-3 x y-y^2+4 x+7 y+C=0$