This You Must Still Think Yourself, CAS Can Only Help lesson plan also includes:
Have the class learn about and make conjectures about a line intersecting a cubic. In this making conjectures about a line intersecting a cubic instructional activity, students draw lines that intersect a cubic at three different points. Students determine the sum of the intersection points. Students repeat the process for various cubics. Students make a conjecture that the sum of the three x-values of the intersection points is always -a.