Cartesian Plane and Linear Equations in Two Variables. Math 021. The Cartesian Plane (coordinate grid) is a graph used to show a relationship between two variables. The horizontal axis is called the x-axis. The vertical axis is called the y-axis.
y – 2x = -3 y = 2x + 7
4x + 5y = -1 Line 2 contains points (8,5) and (2,4)