Working with negative numbers is an important skill in math. Negative values are commonly used with scales that go below zero, such as the Fahrenheit scale for temperature. Decreasing a quantity can be treated as a negative increase. The TI-84 Plus, a graphing calculator, has a special key you use to enter a negative number.

Turn on the calculator by pressing the "ON" key in the bottom left corner.

Press the (-) key in the bottom right corner to make a negative sign. It does not work to use the subtraction button as a negative sign.

Enter a number using the keyboard. For example, pressing (-) and then 3 will display "-3," which corresponds to the value of negative three.

Enter in the rest of your calculation. You can use the same mathematical operations for negative values as you would with positive values.