Salli went to a CD store to buy some CDs. She found that, at this particular store, each CD costs $12.00, with tax included. She had $50.00 in her pocket and wanted to know how much change she would get back if she purchased a certain number of CDs. So she created the following chart:
number of CDs purchased 
change 
0 
$50.00 
1 
$38.00 
2 
$26.00 
3 
$14.00 
4 
$2.00 
The graph to the left is a graph of the function c = 50
 12n. This is a linear function since the graph of the solutions
above results in a straight line.
The red points at left are the some of the solutions to the
equation: y = x^{2}. Note that the red points do not fit onto a line.
Thus y = x^{2} is not a linear function. We say y = x^{2} is a
nonlinear function.
