1-4 adding and subtracting integers

1-4 adding and subtracting integers Ms. Battaglia – algebra 1 CP Objective: add and subtract with integers and decimals, find absolute value, and evaluate expressions.

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

definition • The sum of a number and its opposite, or additive inverse, is zero.

example • On 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. • – 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|

example • Find the absolute value. • |- 12| • | 3.5| • |-5 + 3|

Examples • Evaluate 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. • - 6 – 2 • 8 – ( - 1) • 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!

1-4 adding and subtracting integers