Subtraction with Negative Numbers
1. Definition of subtraction: If a and b are any two numbers, then it is
true that:
a - b = a + ( -b )
Note: Subtracting a number is the same as adding its opposite.
Ex: Write each of the given subtraction problems as an equivalent
addition problem using the definition of subtraction.
a. 14 - 7 = 14 + (-7 )
b. 9 - 4
c. -13 - 5
2. Subtraction with negative numbers:
To subtract two numbers,
rewrite the expression as "addition of the opposite", and then
apply the addition rules.
Ex: Simplify:
a.
| 7 - (-5 ) |
|
|
| |
= 7 + 5 |
change subtraction to addition of the opposite |
| |
= 12 |
apply rule for adding numbers that have the same sign |
b.
| (-8) - (-5 ) |
|
|
| |
= (-8) + 5 |
change subtraction to addition of the opposite |
| |
= -3 |
apply rule for adding numbers that have the same sign |
