# How to Graph a Function on the TI-89

The TI-89 is a powerful, hand held graphing calculator that can save you hours of time on calculus homework. One of the most basic requirements in any calculus class is the ability to graph any function. A function is a type of equation that produces one — and only one — output (“y”) for every input (“x”).

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

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

Sample 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.

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:
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.

## How to Evaluate a Function

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

Sample problem: Evaluate the following function at x = 3: f(x) = x^2 + 5x + 4

Step 1: Press thediamond (♦) 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!

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