Subtracting Integers

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Subtracting Integers
Section 2.3
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To subtract integers, rewrite the subtraction
problem as an addition problem. Study the
examples below.
9 5 4 9 (- 5) 4
Since both expressions
equal 4, we can say
9 5 9 (- 5) 4
Martin-Gay, Prealgebra, 5ed
3
Subtracting Two Numbers
If a and b are numbers, then a b a (-b).
To subtract two numbers, add the first number to
the opposite (called additive inverse) of the
second number.
Martin-Gay, Prealgebra, 5ed
4
subtraction first number opposite of second number

7 4 7 (- 4) 3
- 5 3 - 5 (- 3) - 8
3 (- 6) 3 6 9
- 8 (- 2) - 8 2 - 6
Martin-Gay, Prealgebra, 5ed
5
Adding and Subtracting Integers
If a problem involves adding or subtracting more
than two integers, rewrite differences as sums
and add. By applying the associative and
commutative properties, add the numbers in any
order.
9 - 3 (-5) - (-7) 9 (-3) (-5) 7
6 (-5) 7
1 7
8
Martin-Gay, Prealgebra, 5ed
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Evaluating Algebraic Expressions
Evaluate x - y for x - 6 and y 8.
Replace x with - 6 and y with 8 in x - y.
x - y
( ) - ( )
- 6
8
- 14
Martin-Gay, Prealgebra, 5ed