To enter an equation into a calculator, you may need to enter the "x" variable. X is a common variable and is used in many mathematical expressions including linear equations and polynomials in algebra, geometry and other areas of math. On a graphing calculator, a value can be assigned to the variable x so that when it is used in an expression, the value will be substituted for the variable.
Insert "x" in a mathematical expression

Enter the characters leading up to the x variable in the calculator. You may need to do this in the equation editor or on the main window of the calculator, depending on what you are going to do with the expression. To get to the equation editor on a TI89, press the green diamond button and then the "F1" button. To get to the main screen on a TI89, press the "Home" button. For example, to enter y = 3x + 1 in the equation editor on a TI, start by pressing the green diamond button and then the "F1" button. Type "3" after the "y1=" on the screen.

Press the "X" button. It is located below the "HOME" button and above the "=" button on a TI89. In the example, press the "X" so that you have "3x."

Enter in the characters after the x variable to complete the expression. In the example, first press the "+" key and then "1."
Store a value for the variable "x"

Type the value for "x." For example, if x = 2, type "2" on the home screen.

Press the store button. On a TI89 this is the "STO>" button. In the example, you would see "2>."

Press the "X" button. It is located below the "Home" button and above the "=" button on a TI89.

Press "Enter" to save the value. The next time the x variable is used in an expression, it will be replaced with a 2.