Learning goals: Teacher Facing Recognize that adding or subtracting equations in a system creates a new equation with a solution that coincides with that of the original system, so the new equation can be used to solve the original system. Solve systems of equations by adding or subtracting the equations strategically to eliminate a variable. Use graphing technology to graph the sums and differences of the equations in a system, and analyze and describe (orally and in writing) the behaviors of the graphs. Full lesson plan (warm-up, activities, synthesis, cool-down prompt) from Alg1.2 Linear Equations, Inequalities, and Systems, Algebra 1.