How to Enter Functions on the TI-84 Plus
Before you can graph a function, you must enter it into the TI-84 Plus graphing calculator. The calculator can handle up to ten functions at once, Y1 through Y9 and Y0. To enter functions in the calculator, perform the following steps:
Press [MODE] and put the calculator in Function mode.
To highlight an item in the Mode menu, use the
keys to place the cursor on the item, and then press [ENTER]. Highlight Func in the fourth line to put the calculator in Function mode.
Press [Y=] to access the Y= editor.
Enter the definitions of your functions.
To erase an entry that appears after Yn, use the
keys to place the cursor to the right of the equal sign and press [CLEAR]. Then enter your definition for the new function and press [ENTER].
When you’re defining functions, the only symbol the calculator allows for the independent variable is the letter X. Press
to enter this letter in the definition of your function. Here, this key was used to enter the functions Y1, Y2, Y4, Y5, and Y6.
As a timesaver, when entering functions in the Y= editor, you can reference another function in its definition. (For example, the function Y3 is defined as –Y2.) To paste a function name in the function you’re entering in the Y= editor, follow these steps:
to access the Y-Variables menu.
Press  to access the Function menu.
Press the number key for the name of the function you want to paste in the definition.