Bellwork Sept. 23, 2010 Copy the equations and

SHOW YOUR WORK!Determine if the given numbers are solutions to the given equations.

1. x = 2 for 4x = 9

2. x = 5 for 8x + 2 = 42

3. x = 4 for 3(x – 2) = 10

no

yes

no

1-11 Addition and Subtraction Equations

pg. 52

EQ:How can you solve equations by using subtraction or addition?

DefinitionsAddition Property of Equality- same number is added to both sides of an equation, then the equation remains equal

inverse operations- one operation undoes the effect of the other operation

Subtraction Property of Equality- if both sides of an equation have the same number subtracted from them, the remaining expressions is still equal

To solve an equation means to find a solution to the equation which is done by isolating the variable, (get the variable alone on one side of the equal sign.)

x + 5 = 87 = 3 + y

The variables are isolated.

The variables are not isolated.

x = 8 – 57 – 3 = y

An equation is like a balanced scale. If you increase or decrease the weights by the same amount on both sides, the scale will remain balanced. If you increase or decrease only one side then the scale is not balanced.

Equations with Variables Brain-Pop http://www.brainpop.com/math/algebra/equationswithvariabl

es/

Write down 2 facts from the clip… 1. 2.

You can add the same amount to both sides of an equation, and the statement will still be true.

2 + 3 = 5+ 4 + 4

2 + 7 = 9

ADDITION PROPERTY OF EQUALITYADDITION PROPERTY OF EQUALITY

Words Numbers Algebra

x = y+ z = + z

x + z = y+ z

You can subtract the same amount from both sides of an equation, and the statement will still be true.

4 + 7 = 11 –3 – 3

4 + 4 = 8

SUBTRACTION PROPERTY OF EQUALITYSUBTRACTION PROPERTY OF EQUALITY

Words Numbers Algebra

x = y– z = – z

x – z = y – z

Use inverse operations when isolating a variable.

•Addition is inverse for subtraction

•Subtraction is inverse for addition

•Multiplication is inverse for division

•Division is inverse for multiplication

Step for solving equations

1. Isolate the variable2. Solve for the variable3. Check your answer by substituting

your answer into the first equation.

Solve the equation b – 7 = 24. Check your answer.

Example 1

b – 7 = 24+ 7 +7

b + 0 = 31

Check

b – 7 = 24

31 – 7 = 24

24 = 24b = 31

b = 31

Solve the equation t + 14 = 29. Check your answer.

Example 2

t + 14 = 29– 14 – 14

t + 0 = 15

Checkt + 14 = 29

15 + 14 = 29

29 = 29t = 15

t = 15

The Falcons scored 13 points in a game against the Cowboys. They scored 7 points for a touchdown and the rest of their points for field goals. How many points did they score on field goals?

Example 3- Real World

Let f represent the field goal points.

7 points + field goal points = points scored

7 + f = 13– 7 – 7

f = 6

They scored 6 points on field goals.

PracticeTextbookPage 54 8-24 even only

Practice+36 +36

n + 0 = 53

n = 53

+56 +56p + 0 = 68

p = 68

+51 +51m + 0 = 74

m = 74

-15 -15

x + 0 = 28

x = 28

-14 -14

a + 0 = 24

a = 24

-47 -47

x + 0 = 35

x = 35

Number of books + number of extra books = total read

6 + b = 8-6 -6

b = 2

Work SessionTextbookp. 54 26-42 evenGRADED

Closing

What are two rules to remember when adding and subtracting in equations?

Homework Workbook Page 11 All problems STUDY TEST TOMORROW