Working with negative numbers is an important skill in math. Negative values are common with scales that go below zero, such as the Fahrenheit scale for temperature. You can treat a decreasing quantity as a negative increase. The TI-84 Plus, a graphing calculator, has a special key you use to enter a negative number.
Turn on Calculator
Turn on the calculator by pressing the "ON" key in the bottom left corner.
Enter Negative Sign
Press the (-) key in the bottom right corner to make a negative sign. Be aware that the subtraction button does not work as a negative sign.
Enter Numerical Value
Enter a number using the keyboard. For example, pressing (-) and then 3 will display "-3," which corresponds to the value of negative three. You can make a number of any size a negative number.
Enter the rest of your calculation. You can use the same mathematical operations for negative values as you would with positive values.
TL;DR (Too Long; Didn't Read)
If you only have a basic calculator, look for a button with a "+" sign above a "-" sign, which is often between the 0 and the decimal point. Press this button before the number button to make it a negative number.