In this section we will discuss the method of graphing an equation in two variables. Graphs are used because a picture usually makes the number facts more easily understood. You can usually find examples of these graphs in the financial section of a newspaper. There are many types of graphs, such as bar graphs, circular graphs, line graphs, and so on.
![coordinate picture graphing coordinate picture graphing](https://www.math-salamanders.com/image-files/coordinate-plane-worksheets-find-and-plot-2.gif)
The plane is divided into four parts called quadrants. Thus the plane extends indefinitely in all directions.
![coordinate picture graphing coordinate picture graphing](https://i.pinimg.com/originals/e1/ac/ec/e1acec58d34f379190837335ed10eedf.jpg)
The arrows indicate the number lines extend indefinitely. Positive is to the right and up negative is to the left and down. The zero point at which they are perpendicular is called the origin. The horizontal line is the x-axis and the vertical is the y-axis.
![coordinate picture graphing coordinate picture graphing](https://i.pinimg.com/originals/4c/d2/c0/4cd2c0c670f982e57b076afc0c23bf46.gif)
Study the diagram carefully as you note each of the following facts.
![coordinate picture graphing coordinate picture graphing](https://free-printablehq.com/wp-content/uploads/2019/07/graphingpointsoncoordinateplaneworksheet-preschool-idea-free-printable-coordinate-grid-worksheets.png)
Perpendicular means that two lines are at right angles to each other. This system is composed of two number lines that are perpendicular at their zero points. This scheme is called the Cartesian coordinate system (for Descartes) and is sometimes referred to as the rectangular coordinate system. Rene Descartes (1596-1650) devised a method of relating points on a plane to algebraic numbers. Note that this concept contains elements from two fields of mathematics, the line from geometry and the numbers from algebra. We have already used the number line on which we have represented numbers as points on a line. Given a point on the Cartesian coordinate system, state the ordered pair associated with it.Given an ordered pair, locate that point on the Cartesian coordinate system.Represent the Cartesian coordinate system and identify the origin and axes.Upon completing this section you should be able to: We will now study methods of solving systems of equations consisting of two equations and two variables. In previous chapters we solved equations with one unknown or variable.