1. Lesson 5 SETS-ABSOLUTE VALUE-ADDITION OF SIGNED NUMBERS
A SET is a well defined collection of numbers, objects or things. It is customary to designate a set by enclosing the members of the set within braces.
SUBSETS OF THE SET OF REAL NUMBERS
Natural Numbers = {1, 2, 3, …}
Whole Numbers = {0, 1,2, 3, …} Adds 0 to the set of Natural Numbers.
Integers = {… -1, -2, -3, 0, 1, 2, 3 …} Includes the negatives of every natural number & 0.

2. ABSOLUTE VALUE
Every number except zero has a numerical part and a sign i. e. -7 & +7. The numerical part designates the bigness of the number and we use the words ABSOLUTE VALUE to describe this quality.
We define the ABSOLUTE VALUE of any non-zero number to be a positive number and the ABSOLUTE VALUE of zero to be zero.
We enclose the number within vertical lines to indicate ABSOLUTE VALUE.
Ex.: | 7 | = 7 and also | -7 | = 7

3. ADDITION OF SIGNED NUMBERS
In arithmetic we used a minus sign to indicate subtraction. In algebra we use the minus sign to indicate a negative number.
In algebra the operations of addition and subtraction are lumped together as ALGEBRAIC ADDITION. The sign in front of a number only indicates that the number is either positive (+) or negative (-).
On Line Practice – Adding Signed Numbers
More Practice
And More Practice

4. EXAMPLES: | -5 | | 5.9 | - |12 - 4| -| -13 + 4| (+4) + (+3)
(-5) + (+1)
(-2) + (+4) + (-5 ) + (+7)