De nition 4. For Ka eld, an elliptic curve is a nonsingular cubic curve of genus 1, or, equivalently, is the set of solutions over Kto the following y2 = ax3 + bx2 + cx+ d where a6= 0 and the polynomial in xdoes not have a multiple root. Below are two examples of cubic curves that are not elliptic curves, the rst being y 2= x3 + x and the