Standard - A-REI.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.

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

Standard - A-REI.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 x2 + y2 = 3.

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

Standard - A-REI.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 * 3 or greater).