Subtract real numbers
Recall that the answer to a subtraction problem is called the difference. Thus, the difference between 6 and 4 is 2. To see how subtraction should be defined, compare the following
two statements.
6 – 4 = 2
6 + (-4) = 2
Subtraction
For all real numbers a and b,
a – b = a + (-b).
In words, change the sign of the second number (subtrahend) and add.