Press (Other) and select "1: Define". 

Now type your function. Don't forget to press to get alphabetic characters. I've entered the function f(x) = x^{2}  4 on the screen at right. 

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. 

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

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

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

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