Subtracting Signed Integers

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To subtract two integers, add the opposite of the second integer to the first integer.

In other words, rewrite the subtraction expression as an addition expression and change the second number to its opposite. (e.g. -15 to + 15)

 

Examples

8 - 15 is the same as 8 + (-15)

4 - -2 is the same as 4 + 2

When subtraction occurs several times in an expression, write each subtraction as addition of the opposite and then add.

 

Example

-13 - 5 - (-8)

-13 + (-5) + 8

= -18 + 8

= -10

 

Practice

Find each difference.

1.)     4 - 9

 

 

2.)     -6 - (-7)

 

 

3.)     -2 - 21

 

 

4.)     -42 - (-64) - 13 - 15

 

 

5.)     Find the temperature after a decrease of 5^oC from -19^oC.

Answer Key

1.)  -5

2.)  1

3.)  -23

4.)  -6

5.)  -24 ^oC