Download Section 2.2

Mr. Borosky
Section 2.2
2.2 Add Real Numbers p. 74-79
Algebra 1
Objective: 1. You will add positive and negative numbers.
One way to add real numbers is to use the number line
Key Concept Box p. 75 Rules of Addition
Words
To add 2 numbers with the same sign add
their absolute values. The sum has the
same sign as the numbers added.
To add 2 numbers with different signs
subtract the lesser absolute value from
the greater absolute value. The sum has
the same sign as the number with the
greater absolute value.
Property
Commutative
Examples
8 + 7 = 15
-6 + (-10) = -16
-12 + 7 = -5
18 + (-4) = 14
Properties of Addition
Algebra
Words
a + b = b + a
The order in which you add
3 + (-2) = -2 + 3
2 numbers does not change
the sum
Associative
(a + b) + c = a + (b + c)
(-3 + 2) + 1 = -3 + (2+1)
The way you group 3
numbers in a sum does not
change the sum
Identity
a + 0 = a
or 0 + a = a
-5 + 0 = -5
0 + 8 = 8
The sum of a number and 0
is the number
Inverse
a + (-a) = 0 or –a + a =0
3 + (-3) = 0
-6 + 6 = 0
The sum of a number and
its opposite is 0
Additive Identity – the number 0 since anything plus 0 is itself.
Additive Inverse (Opposite) - numbers that are the same distance from
the origin but on opposite sides of the origin. It is the opposite of
a. Ex. The opposite of -3 is 3, The opposite of 5 is -5, the opposite
of 0 is 0
2.2 Add Real Numbers p. 74-79
Page 1 of 1