A curve called the folium of Descartes is defined by the parametric equations $$x=3t/1+t^3, y=3t^2/1+t^3$$ Show that if (a, b) lies on the curve, then so does (b, a); that is, the curve is symmetric with respect to the line y = x. Where does the curve intersect this line? find all points where tangents are horizonatl or veryocal