A real number less than zero (“0”) is called negative. A negative number is expressed by placing a negative (-) or "minus" sign before the number. Calculations involving negative numbers are important math assignments in the elementary school. Generally, to obtain a negative number you may subtract a positive number from zero. But many scientific calculators have a special function (a key) that allows you to easily obtain a negative counterpart.
Using the "+/-" Key
Enter a number on your calculator; for example, enter "23.5."
Press the key "+/-" on your calculator.
Read the calculator display; the minus "-" appears before the number, indicating that it is negative. In this example, you should read the number "-23.5" on the display.
Enter zero "0" on your calculator if you model does not have the "+/-" key.
Press the key "-" and enter the number, for example "45."
Press the "=" key. The number on the display becomes negative, and you can use it in any further calculation. In this example, the number "45" becomes "-45."