9-1 Graphs of Exponential Functions

The interactive below shows a graph in the form y = a(b)^x with sliders available to adjust the a and b values. Experiment with adjusting the sliders to better understand and see the rules for graphs of exponential functions. What does the graph look like when a is positive or negative? What does the graph look like when b >1 ? What does it look like when 0 < b < 1? Why does the graph go away when b < 0?