Gizmos are a great way to provide conceptual understanding of complex mathematical concepts. Check out these interactive mathematics Gizmos that just received updated Lesson Materials.
In the Addition of Polynomials Gizmo, students use tiles to model and add two polynomials of the form ax2 + bx + c. The Gizmo provides feedback for incorrect steps, and the randomized problem generator allows for unlimited practice to support mastery.
Also, check out the User Lesson Materials from members of the Gizmos community. Kathleen Kaplan submitted a lesson plan for the Addition of Polynomials Gizmo that includes a real-world problem involving the distance between jets, where students will need to subtract polynomials.