A-REI.C. Solve systems of equations.

• Products and Reciprocals

A-REI.C.5. Prove that, given a system of two equations in two variables, replacing one equation by the sum of that equation and a multiple of the other produces a system with the same solutions.

• Solving Two Equations in Two Unknowns

A-REI.C.6. Solve systems of linear equations exactly and approximately (e.g., with graphs), focusing on pairs of linear equations in two variables.

• Accurately weighing pennies I
• Accurately weighing pennies II
• Cash Box
• Estimating a Solution via Graphs
• Find A System
• Pairs of Whole Numbers
• Quinoa Pasta 2
• Quinoa Pasta 3

A-REI.C.7. Solve a simple system consisting of a linear equation and a quadratic equation in two variables algebraically and graphically. For example, find the points of intersection between the line $y = -3x$ and the circle $x^2 + y^2 = 3$.

• A Linear and Quadratic System
• Pythagorean Triples
• The Circle and The Line

A-REI.C.8. Represent a system of linear equations as a single matrix equation in a vector variable.

• No tasks yet illustrate this standard.

A-REI.C.9. Find the inverse of a matrix if it exists and use it to solve systems of linear equations (using technology for matrices of dimension $3 \times 3$ or greater).

• No tasks yet illustrate this standard.