Subtracting Real Numbers

Chapter 2.3

Subtracting is the same as adding a negative!

Warm Up

• What is the opposite of the following?-14 +5.2 -19 19

• What is the absolute value of the following?-14 +5.2 -19 19

• Find the sum-5 + 8= -9 + -12=

Warm Up Answers

• Just change the signs+14 -5.2 +19 -19

• Make them all positive+14 +5.2 +19 +19

• Find the sum-5 + 8= +3 -9 + -12= -21

Subtracting Integers is really adding negatives

• Find the sum 9 + (-6)

• Find the sum 9-(+6)?

• What do you notice about the two number sentences above?

+3

+3

Make a subtraction statement into an addition statement

Exchange the signs in the middle.

4 – (+5) =

-9 – (+8) =

-57 – (+25) =

+87 – (+88)=

A minus sign IS a negative sign.

4 + (-5)

-9 + (-8)

-57 +(-25)+87 + -88

Two negatives make a positive.

4 – (+5) = 4 + (-5)

Opposite

statements

4 – (-5) = 4 + (+5)

Subtract a negative = add a positive.

How do you handle two negative signs in the middle?

-9 – (-8)

Change them both to positive

-9 - (- 8)

-9 + (+8)= -1

Try Some.Rewrite each statement

-57 – (-25)=

-17 – (-21)=

7 – (-13)=

8 – (-33)=

-5 – 15 =

-57 + (+25)

-17 + (+21)

7 + (+13)

8 + (+33)

-5 + -15

And the answer is?

-16 – (-21)=

-83 – (-17)=

83 – (-17)=

47 – (-12)=

-9 – 22 =

-16 + (+21)= -5

-93 + (+17)= -76

83 + (+17)= 100

47 + (+12)= 59

-9 + -22 = -31

pg 71: 23 – 67 odds