https://math.stackexchange.com/questions/3884907/find-tangent-line-common-to-two-hippopedes-curves を 味読し それに 倣い c; 27 x^4+18 x^3 y+12 x^3-12 x^2 y^2-44 x^2 y-17 x^2-2 x y^3-12 x y^2-28 x y-2 x+y^4-20 y^3+85 y^2-6 y=0 が 可約曲線 r…