Functions can be classified in two different categories: linear or nonlinear. A simple way to know differentiate between the two is to look at the output values when plugging in a number for an unknown variable. If the output values have a difference that is constant, then the function will be classified as a linear equation; however, if the outputs do not have a constant difference then it will be classified as a nonlinear equation.
Another easy way to determine which of these functions you are dealing with is to graph it. By graphing these functions, you can tell if the line is straight or not. When graphed, a linear equation will have a straight line that has a constant slope. In contrast to this, a nonlinear equation will have a graph that does not have a straight line and, depending on the function, can have many different appearances including a U-shape or an S-shape.
