Pre-Algebra

2-2 Subtracting Integers

Today’s Learning Goal Assignment

Learn to subtract integers.

Pre-Algebra

2-2 Subtracting Integers

Lesson Quiz: Part 1

1. Write a subtraction equation for the number line diagram.

–4 –3 –2 –1 0 1 2 3 4

Perform the given operations.

2. –6 – (–4)

3. –9 – 4 + (–3)

2 – 3 – 2 = –3

–2

–16

Pre-Algebra

2-2 Subtracting Integers

Lesson Quiz: Part 2

Evaluate each expression for the given value of the variable.

4. 9 – s for s = –5

5. –4 – w + 5 for w = 21

14

–20

Pre-Algebra

2-2 Subtracting Integers

Are we ready for the FAST TRACK?

Pre-Algebra

2-2 Subtracting Integers

Pre-Algebra: 2-2 HW

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Pre-Algebra

2-2 Subtracting Integers2-2 Subtracting Integers

Pre-Algebra

Warm Up

Problem of the Day

Lesson Presentation

Pre-Algebra

2-2 Subtracting Integers

Warm UpAdd.

1. –7 + 2 4. –6 + (–28)

2. –12 + (–9) 5. 104 + (–87)

3. 32 + (–19) 6. –18 + (–24)

Pre-Algebra

2-2 Subtracting Integers

–5 –34

17

–42

–21

13

Pre-Algebra

2-2 Subtracting Integers

Problem of the Day

Copy and complete the magic square. The magic sum is 0.

–8 +3

–2 0

–3

+5

–2

–5+8

Pre-Algebra

2-2 Subtracting Integers

Learn to subtract integers.

Pre-Algebra

2-2 Subtracting Integers

Subtracting a smaller number from a larger number is the same as finding how far apart the two numbers are on a number line. Subtracting an integer is the same as adding its opposite.

SUBTRACTING INTEGERSWords Numbers Algebra

Change the subtraction sign to an addition

sign and change the sign of the

second number.

2 – 3 = 2 + (–3)4 – (–5) = 4 + 5

a – b = a + (–b)a – (–b) = a + b

Pre-Algebra

2-2 Subtracting Integers

Additional Example 1: Subtracting Integers

A. –7 – 4

–7 – 4 = –7 + (–4)

B. 8 – (–5)

8 – (–5) = 8 + 5

C. –6 – (–3)

–6 – (–3) = –6 + 3

= –11

= 13

= –3

Add the opposite of 4.

Add the opposite of –5.

Add the opposite of –3.

Same sign; use the sign of the integers.

Same sign; use the sign of the integers.

6 > 3; use the sign of 6.

Subtract.

Pre-Algebra

2-2 Subtracting Integers

Try This: Example 1

A. 3 – (– 6)

3 – (–6) = 3 + 6

B. –4 – 1

–4 – 1 = –4 + (–1)

C. –7 – (–8)

–7 – (–8) = –7 + 8

= 9

= –5

= 1

Add the opposite of –6.

Add the opposite of 1.

Add the opposite of –8.

Same signs; use the sign of the integers.

Same sign; use the sign of the integers.

8 > 7; use the sign of 8.

Subtract.

Pre-Algebra

2-2 Subtracting Integers

A. 8 – j for j = –6

8 – j

8 – (–6) Substitute –6 for j.

Evaluate the expression for the given value of the variable.

= 8 + 6

= 14

Add the opposite of –6.

Same sign; use the sign of the integers.

Additional Example 2A: Evaluating Expressions with Integers

Pre-Algebra

2-2 Subtracting Integers

B. –9 – y for y = –4

= –9 + 4

= –5

Evaluate the expression for the given value of the variable.

–9 – y

–9 – (–4) Substitute –4 for y.

Add the opposite of –4.

9 > 4; use the sign of 9.

Additional Example 2B: Evaluating Expressions with Integers

Pre-Algebra

2-2 Subtracting Integers

C. n – 6 for n = –2

n – 6

–2 – 6 Substitute –2 for n.

Evaluate each expression for the given value of the variable.

= –2 + (–6)

= –8

Add the opposite of 6.

Same sign; use the sign of the integers.

Additional Example 2C: Evaluating Expressions with Integers

Pre-Algebra

2-2 Subtracting Integers

A. 11 – m for m = –3

11 – m

11 – (–3) Substitute –3 for m.

Evaluate the expression for the given value of the variable.

= 11 + 3

= 14

Add the opposite of –3.

Same sign; use the sign of the integers.

Try This: Example 2A

Pre-Algebra

2-2 Subtracting Integers

B. –5 – r for r = –2

= –5 + 2

= –3

Evaluate the expression for the given value of the variable.

–5 – r

–5 – (–2) Substitute –2 for r.

Add the opposite of –2.

5 > 2; use the sign of 5.

Try This: Example 2B

Pre-Algebra

2-2 Subtracting Integers

C. a – 7 for a = –9

a – 7

–9 – 7 Substitute –9 for a.

Evaluate each expression for the given value of the variable.

= –9 + (–7)

= –16

Add the opposite of 7.

Same sign; use the sign of the integers.

Try This: Example 2C

Pre-Algebra

2-2 Subtracting Integers

The top of the Sears Tower in Chicago, is 1454 feet above street level, while the lowest level is 43 feet below street level. How far is it from the lowest level to the top?

Additional Example 3: Architecture Application

1454 – (–43) Subtract the lowest level from the height.

1454 + 43 Add the opposite of (–43).

= 1497 Same sign; use the sign of the integers.

It is 1497 feet from the lowest level to the top.

Pre-Algebra

2-2 Subtracting Integers

The distance from the high dive to the swimming pool is 10 feet. The pool is 12 feet deep. What is the total distance from the high dive to the bottom of the pool?

Try This: Example 3

10 – (–12) Subtract the depth of the pool from the height of the high dive.

10 + 12 Add the opposite of (–12).

= 22 Same sign; use the sign of the integers.

It is 22 feet from the diving board to the bottom of the pool.