Chapter 3

3.1

Linear EquationsIn 1 and 2 Variables

Use your book glossary to find the definitions

1. EQUATION:

2. LINEAR EQUATION: an equation with exponent of 1 (in 1 variable)

(in 2 variables)

3. INDEPENDENT VARIABLE:

4. DEPENDENT VARIABLE:

A statement of equality between 2 quantities

5. IDENTITY: One side of equal sign is the same as the other. All values of the variable produce a true statement.

6. CONDITIONAL: Equation that is true for only certain

values of the variable.

For the following, decide whether the equation is an identity or conditional and write the answer on the line.

a. x + 2 = 7(can x be anything? Or just one thing?)

b. x – 3 = y(can x be anything? Can y be anything? Or just one

thing?)

conditional

conditional

c. ab = ba

d. P = 2l + 2w

e. 2(x + 4) = 2x + 8

f. 4r – 1r = 3r

Which are equations in 1 variable?

Which are equations in 2 variables?

identity

conditional

identity

identity

Translate the following into equations. Let x be the number.

a.One fourth of a number is 24.

b.A number multiplied by 3 and then added to 6 gets 15.

c.The difference between fourteen and twice a number is

negative 8.

(1/4)x = 24

6 + 3x = 15

14 – 2x = -8

For the following, translate the algebraic equation into an English sentence. Can you think of another way to write the same thing?

x – 2 = -4

9x = 72

2 less than a number is negative four.

Nine times a number is 72.

For the following, define the variables and find the equation

a.The cost of renting a car at $35 flat fee and $0.11 per mile.

b.The total cost of an item bought in Michigan; including tax.

x = number of miles y = cost or renting a car y = 35 + 0.11x

x = ticket cost of an item y = total cost of itemy = x + 0.06x

The next set of sentences contains a phrase that describes a need for grouping symbols. Underline the phrase and then write the equation.

a. Five times the difference between nine and a number is –35.

b. The four times the sum of a number and 5 is 24.

c. The total cost of an air-compressor is $5 for the first day plus $30 for each additional day.

5(9 – x) = -35

4(x + 5) = 24

y = 5 + 30(x – 1)* x= number of days

Birthday Party Exploration

Emma wants to have her birthday party at Valley Bowling Alley. Her mother can rent a party room, let the kids rent shoes and play 3 games for $20 plus $10 per child.

Estimate the total cost if 5 of Emma’s friends come to her party.Estimate the total cost if 15 friends come to Emma’s party. (she must be a very popular girl!)

Explain how you found the costs in #1 and 2.

Write an equation representing the total costs of Emma’s birthday party at Valley Bowling Alley. Let t = the total cost of the bowling alley party (excluding cake, decorations…) and let n = the number of Emma’s friends who attend the party.

t =

Her mother can rent a party room, let the kids rent shoes and play 3 games for $20 plus $10 per child.

Estimate the number of friends Emma can invite for $240. You only need to estimate to answer this

question.

Which variable do you know in #5? Where would you put it, if you wanted to use the equation? Try to set up the equation.

Which variable do you know in #1. Estimate the total cost if 5 of Emma’s friends come to her party.

Try to set up the equation for that situation.

Estimate the total cost if 5 of Emma’s friends come to her party.Do you think these 2 equations are the same of different? Why?

3.2

Solving LinearWith

Algebraic Notation

When my daughter was in 3rd grade, she had a problem that said:

What number is added to 7 to get 15.

I told her, “Emma, think 15 – 7 = ? “15 – 7 = 8”, she said.

“Does 7 + 8 = 15?”She thought for a minute, then “YES!”

What’s My Number ?

When I add 8 to my number, I get 20. What’s my number?

Can you make an equation out of that problem?

What should I tell my daughter to think?

When I divide my number by 2, I get 6. What’s my number?

Can you make an equation out of that problem?

When solving linear equations, we work backwardTo move things across the equal sign to ultimately get the variable by itself.

Reverse the order of operations.

What is the last order of operations?What comes before that?

SOLUTION – a value for the variable that makes the equation true.

3x – 2 = 1 Check for x = 0, x = 1

2 – 6x = 2 Check for x = -1, x = 1, x = 0

SOLUTION SET– all solutions to an equation.

SOLVING – a process where you use inverse operations.

ADDITION PROPERTY for EQUATIONS if a = b, then a + c = b + c.

You can ADD (SUBTRACT)the same thing to both sides of an equation.

MULTIPLICATION PROPERTY for EQUATIONS if a = b, then ac = bc.

You can MULTIPLY (DIVIDE)the same thing to both sides of an equation.

x + 8 = 20 What do you think we need to do 1st ?

x + 8 = 20 -8 -8x + 0 = 12 x = 12

White beans are positive numbers

Black beans are negative numbersve numbersCandy is the variable

White and Black beans cancel each other out.

### x - ##### = -###

##### #####

### x = ##

X = ##/###

MAKE A PLANEQUATION KNOWN? ACTION CHECK

x + 3 = 2 3 is added to x Subtract 3 from both sides

x = -1(-1) + 3 = 2

43

x

921

x

**NOTE: you can change the subtraction on the variable to addition

1. The 2 is added to the variable term 2. x is

multiplied by –6

5 = 2 – 6x

4x = 2

Subtract 2 from both sides

divide both sides by -6

)( 725

67

625

67

x

Look in your book:

Page 133 #56

Page 143 #82, 83, 84

3.3

Solving EquationsTables, Graphs, Symbols

EQUIVALENT – when you do something to both sides it remains equivalent

3x + 5 = 7 is equivalent to 3x = 2 (subtracted 5 both sides)

Tables and Graphs-- give us a numerical and visual picture of what solving an equation means.

Solving Equations With

Tables and GraphsWorksheet

x y = 3x - 2-2013

Solve (by hand)-1 = 3x - 2

0 = 3x - 2

1 = 3x - 2

3 = 3x - 2

CALCULATOR STEPS1. Y =2. 2nd – WINDOW3. TBLSTART = -24. Δ TBL = 1/35. 2nd - Graph

x y = 4 - x

2

0

5

x y = 5 - 3x

-1

0

5

CALCULATOR STEPS1. Y =2. 2nd – WINDOW3. TBLSTART = 04. Δ TBL = 15. 2nd - Graph

CALCULATOR STEPS1. Y =2. 2nd – WINDOW3. TBLSTART = -14. Δ TBL = 1/35. 2nd - Graph

GRAPHS:

4 = 3x - 2

-5 = 3x - 2

1 = 3x - 2

y = 3x - 2See page 147

9 = 3x - 2y=9

y=4

y=1

y=-5

CALCULATOR STEPS1. Y1 = left side2. Y2 = right side3. Window (set it)4. Graph

GRAPHS:

4 = 4 - x

-7 = 4 - x

1 = 4 - x

y = 4 - x

y=4

y=1

y= -7

Go to pg 153 - #10 Book/Calc.

(#18) 3(x– 1) = -3Does this look like linear form yet?What should we do 1st to get to linear

form?

3431

x

(#30) 6 – 5(x – 1) = 31 **can change subtraction to adding a (-)

SYMBOLS: (page 154)

(#26)

x = 0

x = 5

x = -4

How does a table show the solution to the equation?

How does a graph show the solution to the equation?

Which of the 3 methods would you prefer for

5 + 9x = 21?

Which of the 3 methods would you prefer for

5(x – 7)2 + x = 20 ?

Look at y column for what is known and over to x column for answer.

Look at y axis, go across to line, then down to solution off x axis.

Table or Symbols– not a nice round number for graph

Graph or Table – a lot of work for symbols.

WORD PROBLEMS –page 154 # 38, 40, 42

#38 7(x + 3) = - 21

#40 1/3(x + 6) = -2

#42 70 = 10(x – 4) + 30

Mid-Chapter Review: page 155-6 # 2abd, 3, 4, 7, 10, 15, 19ad, 20

3.4

Solving Linear EquationsWith

Variables on BOTH sides

White beans are positive numbersBlack beans are negative numbersCandy is the variable

White and Black beans cancel each other out.

Balance Beans

Try these in your group:3x – 1 = x + 1

5x + 6 = 3x + 2

6x – 6 = 10 – 2x

TRY: 2(x + 1) = 4x - 8

3x – 5 = -3 + x

# # # x - # # # # # = - # # # + # x- #x___________________ - #x ## x - # # # # # = - # # #

## x - # # # # # = - # # # + # # # # # +# # # # # # # x = # #

X = # #/# # = #

Solving Symbolically

6 – 5x = 3(1 – x)Always clear parentheses 1st

Collect all variables on 1 sideAdd 5x to both sides-why?

Collect all constants on the other side.

Solve for x.

Calculator TechniquesWorkSheet

APPLICATIONS

Page 165# 46

U-Haul Budgety = 39.95 + 1.59x y = 69.99 + 0.89x

In New York City, a U-Haul 24-foot moving truck costs $39.95 plus 1.59 per mile for 6 hours. The same truck from Budget costs $69.99 plus $0.89 per mile.

State the equation by setting the two cost equations equal to each other.

Solve and explain the meaning of the solution.

What does the output of the point of intersection mean?

Tables and Graphs Worksheet(in groups)

Look at Warm-Up Page 166

3.5

Solving Linear InequalitiesIn 1 Variable

SYMBOLICFOR THE FOLLOWING, DETERMINE IF THE INEQUALITY IS TRUE OR FALSE AFTER THE OPERATION IS DONE.

4 < 10 ADD 2 to both sides. True/False

4 < 10 ADD -2 to both sides True/False

4 < 10 MULTIPLY 2 to both sides. True/False

4 < 10 MULTIPLY -2 to both sides. True/False

4 < 10 DIVIDE 2 to both sides. True/False

Try -2. True/False

GENERAL RULE for INEQUALITIES

The inequality stays the same when adding and subtracting across the inequality sign.

The inequality ONLY CHANGES when you Multiply or Divide both sides by a negative number.

TABLES

x – 1 < 2x y =x - 1 y = 2

1 0 2

2 1 2

3 2 2

4 3 2

5 4 2

Find where they are the sameLook at the behavior of the numbers before and after that point

What set of values makes the inequality true?

Let’s graph on a number line:

0 2 4

Which side of 2 makes a true statement? Test the points on either side

Look at graphs

TABLES

5 < 2 – 3xx y = 5 y = 2 – 3x

-3 5 11

-2 5 8

-1 5 5

0 5 2

1 5 -1

Find where they are the sameLook at the behavior of the numbers before and after that point

What set of values makes the inequality true?

Let’s graph on a number line:

-3 -1 0

Which side of -1 makes a true statement? Test the points on either side

Look at graphs

Try: 3 – 3x > 2 – 2x

GRAPHS

Find the point of intersection

Check to see which graph has the larger y values BEFORE the intersection

Look what happens to the y values of that line AFTER the intersection

Which side of the intersection would make the inequality true?

APPLICATIONSThe graph below represents the profit for Companies A and B if they sell x units of their product.

Amount of Product

Company A Profit

Company B Profit

20,000

45,000

Complete the following table by using the graph to estimate.

1. Which company has the larger profit when 20,000 units are produced?

2. Which company has the larger profit when 45,000 units are produced?

3. Approximate from the graph, when the two companies’ profits are equal.

4. How many units must be sold for Company A’s profits to be larger than Company B’s profits?

GROUP WORK

END OF CHAPTER 3