1. Algebra 1
Section 1.3

2. Addition The numbers being added are called the addends
The answer to an addition is called the sum

3. Same Signs on Addends Add the absolute values of the addends.
Give the sum the sign of the two addends.

4. Different Signs on Addends
Subtract the smaller absolute value from the larger absolute value.
Give the difference the sign of the addend with the larger absolute value.

5. Example 1
a = ____
b (-3) = ____ 5 -4

6. Example 2
a. 3 + (-2) = ____
b = ____ 1 -2

7. Example 3 a. -1 + (-3) = ____ b. 8 + (-3) = ____ c. 4 + (-10) = ____-4 -5 -6

8. Definition
A mathematical property or identity is an equation or statement that is true for any value of the variable.

9. Properties of Addition
Commutative Property: If you add two numbers together in different orders, the sum is the same.
a + b = b + a

10. Properties of Addition
Associative Property: If you group numbers together differently when adding, the sum is the same.
(a + b) + c = a + (b + c)

11. Properties of Addition
Additive Identity Property: The sum of any number and zero is that number.
a + 0 = 0 + a = a

12. Properties of Addition
Additive Inverse Property: The sum of any number and its additive inverse (opposite) is zero.
a + (-a) = 0

13. Example 5 -1 + 5 + (-3) + (-7) + 4 + (-6)
(-1) + (-3) + (-7) + (-6)
9 + (-17) -8

14. Example 5 8 + (-3) + 15 + (-8) 8 + (-3) + 15 + (-8)
8 + (-8) + (-3) + 15
0 + 12 12

15. Homework: pp