Lines That Cross

Solving systems by graphing

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• An equation in two unknowns is a line of solutions.
• A system’s solution is where the lines cross; parallel lines mean no solution.
• Break-even and catch-up problems are line crossings.

Steps

1. Every equation is a line
2. Find the crossing
3. Phone plans
4. Lines that never meet
5. Where they meet
6. Catching up