What is the plane curve proposed by Descartes to challenge Fermat's extremum-finding techniques called?

The plane curve proposed by Descartes to challenge Fermat's extremum-finding techniques is called the Folium of Descartes. This curve is a type of algebraic curve defined by the equation x^3 + y^3 - 3axy = 0, where a is a constant parameter. Descartes used this curve to challenge Fermat because it possesses two points of inflection, which make it difficult to determine the maximum or minimum values of certain functions. This curve demonstrated the limitations of Fermat's techniques and led to the development of new mathematical methods for solving extremum problems.