Adding Integers 3-2
Chapter 3-2 Adding
Integers
Integers like 2
and -2 are called opposites
Two integers that
are opposites are also called Additive Inverses
ADDITIVE INVERSES:
When the two
addends are OPPOSITE SIGNS of the SAME AMOUNT, the sum is ZERO.
I say: Additive
Inverses…YAY! Because looking for them, makes the math easier.
Who wins? NO ONE!
IT’S A TIE!!!
Additive Inver
Property- the sum of any number and its addivitve inverse ( opposite) is ZERO
Adding Integers
The rules:
SAME SIGN: Just
add and keep the sign
4 + 5 = 9 and -4 + (-5) = -9
-14 + (-16) = -30
DIFFERENT SIGNS:
Don’t add! Take the difference (subtract) and take the sign of the bigger
absolute value
When adding
integers with different signs—DON’T ADDà take the difference and use the sign of the larger absolute
value!!
I SAY:
WHO WINS? (which
number [absolute value] is bigger?)
BY HOW MUCH?
(you’ll automatically take the difference)
When you play a
game, you know if you won or not
AND
You know how much
you either won or loss by!
ALWAYS “
STACK ‘EM”
-8 + 20
Who won?
The positive team
By how much?
12!
Does it work with
same signs?
Yes, because only
one team came to play ;)
-8 + (-20)
Who won?
Only the negative
came to play so the negatives
By how much?
Since they’re on
the same team, just add up the players’ scores
TWO MORE WAYS TO
UNDERSTAND ADDING INTEGERS:
1. A positive/
negative sketch
Represent each
positive number with the appropriate number of + signs
Represent each
negative number with the appropriate number of – signs
Place them on
different rows
Box in the number
that match and cross them out…they are ADDITIVE INVERSES and equal 0
Whatever is left
OUTSIDE the box, is the answer
-3 + 5
- - -
+ + + + +
The answer is +2
2. A number line
The positive
direction is right
The negative
direction is left
Remember: Due to
our BFF the Commutative Property of Addition, you can do addition in any order
that’s easiest!
-8 + 12 + (-4)
becomes
-8 + (-4) + 12
Then add the first
two addends
-12 + 12 = 0
Simplify
w + (-4) + 2 = w +
(-2)
7 + a + -7 = a
