1-4 ADDING AND

SUBTRACTING IN

TEGERS

M S . BA T T A G L I A

– A

L G E B R A 1 C

P

O B J EC T I V

E : AD D A

N D SU B T R A C T W

I TH

I NT E G E R S A

N D DE C I M

A L S , FI N

D AB S O L U T E

V A L U E , AN D E

V A L U A T E EX P R E S S I O

N S .

WARM UP

Simplify.

EXAMPLE…You’re at the supermarket and have $4.25 in your

pocket. The groceries you buy cost $3.12. How much money do you have left?

The groceries you want to buy cost $5.63. How much money do you owe?

ADDING INTEGERS AND DECIMALSA number line can help you see the relationship between numbers.

Opposites - same distance from zero on the number line.

Integers - whole numbers and their opposites.

1) What is the opposite of 3? -5? -100? 0?2) Name the 2 integers that are a distance of 7 unites from 0.

DEFINITIONThe sum of a number and its

opposite, or additive inverse, is zero.

EXAMPLEOn two plays, a football team gains 2 yd

and then loses 7 yd. What is the result of the two plays?

ADDITION RULES…To add two numbers with the same sign, add

their absolute values. The sum has the same sign as the numbers.

Examples: 3 + 5 = (- 3) + (- 5) =

To add two numbers with different signs, find the difference between their absolute values. The sum has the same sign as the number with the greater absolute value.

Examples: - 3 + 5 = ( 3) + (- 5) =

FIND EACH SUM.

a)– 6 + 4

b) - 3 + ( - 8)

c) 4 + (- 6)

d) 9 + (- 3)

ABSOLUTE VALUE

The absolute value of a number is its distance from zero on a number line.

Using symbols, you write the “absolute value of – 6” as |- 6|

EXAMPLEFind the absolute value.

a) |- 12|

b) | 3.5|

c) |-5 + 3|

EXAMPLESEvaluate each expression for n =

3.5

a) 5.2 + n b) – 5.2 + n

SUBTRACTION RULE…

To subtract a number, add its opposite.Example: 3 – 5 =

EXAMPLE

Find each difference.

a) - 6 – 2

b) 8 – ( - 1)

c) 3 - 13

CLASSWORK

P. 20-22 #6bd, 11, 12cd, 15bcd, 16, 17

HOMEWORK

P. 22-23 #3-7 odd, 8,10,12,29,30, 35

QUIZ IN 2 DAYS!