Page 38 - Algebra 1

Exploration Modeling Real Number Addition Find the sum -5 + 3.
Model -5 and 3 using algebra tiles.
----- +++ Group positive and negative tiles to make zero pairs.
----- +++
Count the remaining tiles.
-5 + 3 = -2 Model -5 + 3 on a number line.
+3
-6 -4 -2 0 2
Use algebra tiles to find the sum. Then model each problem on a
number line.
a. 4+(-3) b. -2+-6 c. (-7)+7
Generalize Determine whether each statement is true or false. Provide a counterexample for false statements.
d. The sum of two positive numbers is always positive.
e. The sum of two negative numbers is always negative.
f. The sum of a positive and a negative number is always negative.
The sum of two numbers can also be found using the rules for adding real numbers. These rules apply to all real-number addends.
Hint
+=1
- = -1 ++-=0
-5
Rules for Adding Real Numbers
Adding Numbers With the Same Sign
To add numbers with the same sign, add their absolute values. The sum will have the same sign as the addends.
Examples 3 + 2 = 5 -3 + (-2) = -5
Adding Numbers With Different Signs
To add numbers with different signs, find the difference of their absolute values. The sum will have the sign of the addend with the greater absolute value.
Examples 3 + (-2) = 1 (-3) + 2 = -1
Online Connection www.SaxonMathResources.com
Lesson 5 23