How to Evaluate a Function on the TI-84 Evo

The TI-84 Evo lets you save a function once and evaluate it at any input, so you don't have to retype the expression every time.

Save your function in Y=

  1. Press y= to open the function editor. The cursor starts on the Y1 line. (If you already have a function in Y1 from graphing, you can skip this step.)
  2. Type your function. For this example, type 2X+1. The X key is just to the right of alpha.
    The Y= editor on the TI-84 Evo with Y1=2X+1 entered

Evaluate from the home screen

Instead of retyping 2(3)+1 every time, you can call Y1 by name. The vars key is next to clear:

TI-84 Evo keyboard with the vars key highlighted, next to clear
  1. Press vars, then arrow right to the Y-VARS tab.
    The VARS menu on the Y-VARS tab, showing 1:Function highlighted
  2. Press enter to select 1:Function. A list of function names appears.
    The Function submenu showing Y1 through Y9, with Y1 highlighted
  3. Press enter again to select Y1. It pastes "Y1" onto the entry line.
  4. Type ( then the value you want and press enter. For x=3, type (3 and press enter.
    The home screen showing Y1(3 = 7

Y1(3) gives 7, which is 2(3)+1. Repeat the same steps to evaluate at any other value.

Good to know

  • You don't need to close the parenthesis. Y1(3 then enter works the same as Y1(3). Close the parenthesis only when more follows it, like Y1(3)+Y1(5).
  • For a whole batch of values, use a table. The table evaluates your Y1 function at every x in a range automatically.
  • You can evaluate on the graph, too. Graph the function, then press 2nd+trace and choose 1:value to evaluate at any x you type.
  • Multiple functions work the same way. Enter a second function on the Y2 line, and call it with Y2(value) through the same VARS menu.