In this article, we are going to learn how to graph equations on a Cartesian coordinate plane. We are already familiar from a previous article how to graph ordinary ordered pairs such as (2, 5) or (3, 5) on a coordinate plane. But what about equations? In order to figure out how to graph an equation, we must determine what sorts of input values satisfy the variable of an equation.
For example, suppose that we have the equation y = 4x + 10. Suppose y = 18 and x = 2. This would make the equation true, since 4(2) = 8 + 10 = 18, which is what y is equal to. There are an infinite number of pairs which make this equation true. Indeed, to graph an equation means nothing other than to graph the points of ordered pairs that make an equation true. A graph of an equation that forms a straight line is called a linear equation. "Linear" refers to a line. This is precisely why it is called a linear equation.