In some math problems like the equation for a line, there can be more than one variable ("x" and "y" in this case). To find points on the line, one variable is changed. The variable that is changed is called the "independent" variable. Then the math is done to make a number. The number that is made is called the "dependent" variable. Most of the time the independent variable is written as "x" and the dependent variable is written as "y", for example, in y = 3x + 1. This is often put on a graph, using an "x" axis (going left and right) and a "y" axis (going up and down). It can also be written in function form: f(x) = 3x + 1. So in this example, we could put in 5 for "x" and get y = 16. Put in 2 for "x" would get y=7. And 0 for "x" would get y=1. So there would be a line going thru the points (5,16), (2,7), and (0,1) as seen in the graph to the right.