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Algebra 1
Section 1.3
Addition
The numbers being added are
called the addends
The answer to an addition is
called the sum
Same Signs on Addends
1. Add the absolute values of
the addends.
2. Give the sum the sign of
the two addends.
Different Signs on Addends
1. Subtract the smaller
absolute value from the
larger absolute value.
2. Give the difference the sign
of the addend with the
larger absolute value.
Example 1
a. 3 + 2 = ____
5
-4
b. -1 + (-3) = ____
Example 2
a. 3 + (-2) = ____
1
-2
b. -7 + 5 = ____
Example 3
a. -1 + (-3) = ____
-4
-5
b. 8 + (-3) = ____
c. 4 + (-10) = ____
-6
Definition
A mathematical property or
identity is an equation or
statement that is true for any
value of the variable.
Properties of Addition
Commutative Property: If you
add two numbers together in
different orders, the sum is the
same.
a+b=b+a
Properties of Addition
Associative Property: If you
group numbers together
differently when adding, the
sum is the same.
(a + b) + c = a + (b + c)
Properties of Addition
Additive Identity Property: The
sum of any number and zero is
that number.
a+0=0+a=a
Properties of Addition
Additive Inverse Property: The
sum of any number and its
additive inverse (opposite) is
zero.
a + (-a) = 0
Example 5
-1 + 5 + (-3) + (-7) + 4 + (-6)
5 + 4 + (-1) + (-3) + (-7) + (-6)
9 + (-17)
-8
Example 5
8 + (-3) + 15 + (-8)
8 + (-8) + (-3) + 15
0 + 12
12
Homework:
pp. 16-17