# Graph a Function on the TI-89 & Evaluate

Feel like "cheating" at Calculus? Check out our Practically Cheating Calculus Handbook, which gives you hundreds of easy-to-follow answers in a convenient e-book.

Contents:

## How to graph a function on the TI-89: Steps

You can graph a function on the TI-89 graphing calculator in a snap with these simple steps:

Example problem: Graph the following function:
f(x) = x2 + 8x

Step 1: Press the HOME key.

Step 2: Press the diamond key and then press the F1 key to enter into the y=editor. Location of the F1 and diamond keys.

Step 3: Press ENTER to move to the input line at the bottom of the screen.

Step 4: Press the following keys to enter the example function into a “y=” slot (don’t type the “y=” because it’s already there! Make sure to only type the right hand side of your equation):
x ^ 2 + 8 x ENTER.

Step 5: Press the diamond key and then press the F3 key to view the graph of the function.

That’s it! You’re done!

## Help! My Graph isn’t Showing!

If your graph is not showing on the screen, try these tips:

1. Double check to make sure you’ve entered the function correctly.
2. Make sure the function isn’t turned off. In the y = editor window, pressing F5 and making a selection will turn a function off. F4 and selecting a function will turn the function on. You want to make sure your entered function is ON.
3. Use the zoom feature (F2 and then 2 or 3) to zoom in and out of the graph. This will automatically adjust the viewing window.
4. Try the “standard zoom”—setting the window to -10,10 for both the y and x values. You can also try zoombox.

Still having trouble? Check out the TI-89 Error Codes.

## How to Evaluate a Function

Once you’ve entered your function, you will need to know how to evaluate the function at certain values.

Example problem: Evaluate the following function at x = 3: f(x) = x2 + 5x + 4

Step 1: Press the diamond button and then press F1 to enter the y=editor.

Step 2: Press the ENTER key to go down to the entry field for y1.

Step 3: Press x ^ 2 + 5 x + 4.

Step 4: Press the ENTER key to enter the function into the “y1” slot.

Step 5: Press the ENTER key.

Step 6: Evaluate the function at x = 3 by pressing Y1(3).

Step 7: Press the ENTER key. The answer you see should be 28.

That’s it! You’re done!

## References

Larson, R. & Edwards, B. (2016). Calculus, 10th Edition. Cengage Learning.

CITE THIS AS:
Stephanie Glen. "Graph a Function on the TI-89 & Evaluate" From CalculusHowTo.com: Calculus for the rest of us! https://www.calculushowto.com/how-to-graph-a-function-on-the-ti-89/
---------------------------------------------------------------------------  Need help with a homework or test question? With Chegg Study, you can get step-by-step solutions to your questions from an expert in the field. Your first 30 minutes with a Chegg tutor is free!