Having taught MAT151 (College Algebra) in both Fall 2011 and Spring 2012, I noticed that a fair number of students were having difficulty understanding the concept of a function. Many failed to recognize how a function's output value varies in a predictable way based on changes to its input value, and most had a hard time connecting the geometric, tabular, verbal and equation representations of a function. Developing this understanding is critical to student success in MAT151 and subsequent math classes. Based on my experience with the District's Modular Math Redesign effort over the summer, I decided to include an interactive software tool in my Fall 2012 classes along with extensive TI-84 calculator examples. GeoGebra is an open-source interactive tool that gives students a way to see how a function's graph relates to its equation as well as to a point table. They can manipulate one representation of the function and observe the changes in the other representations. Since there is already a large GeoGebra user base, many relevant examples were already available online. Examples and final grade comparisons are attached.