Solution 12141: Graphing and Evaluating Exponential Functions Using the TI-89 Family, TI-92 Family, and Voyage™ 200 Graphing Calculators.
How can I graph and evaluate an exponential function using a TI-89 family, TI-92 family, or Voyage 200 graphing calculator?
To graph an exponential function, refer to the steps below:
• Press [◊] [Y=] to go to the Y= editor
• Press [2nd] and [ex]
• Press [X] then press [)] to close the parentheses
• Press [ENTER] (screen should read y1= ex)
• Press [◊] [GRAPH] to display the exponential curve
While on the graph screen, you can then evaluate the exponential function at any value of x. This can be used to find the y-intercept of the function by evaluating it at x=0. The following demonstrate how this is done on the calculator:
• Press [F5]  to select 1:Value from the Math menu
• Input the desired value of x (0 in this example)
• Press [ENTER] to display the corresponding y-coordinate
Please see the TI-89 family, TI-92 family and Voyage 200 guidebooks for additional information.