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Use f(x) Notation

on the TI-89

The TI-89 makes it easy to handle functions in f(x) notation. This is great for exploring and checking your work on homework problems.


Press F4 key(-Other) and select "1: Define".

F4 1: Define Menu

Now type your function. Don't forget to press alpha key to get alphabetic characters. I've entered the function f(x) = x2 - 4 on the screen at right.

f(x) = x^2 - 4

As you can see at right, the calculator can evaluate the function at any (legal) value, such as f(5), f(a), f(2t - 1) using the normal mathematical notation.

f(5), f(a), and f(2t-4)

It is also straightforward to graph y = f(x), as shown at right. Just press diamond keyf1 key, and type "f(x)" enter key..

y= f(x)

Here is the graph of y = f(x), made by pressing f2 key(-Zoom) and selecting "6: ZoomStd"

graph of y = f(x)

You can also define a function by entering it in the "Y=" (f1 key) screen.

y1 = x^2 - 4

You can evaluate functions defined on the "y=" screen in exactly the same way as a function defined on the home jey screen.

y1(5), y1(a), y1(2t-1)

last update June 29, 2004 by JL Stanbrough