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2.1

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2.1

Linear Functions and Models

- We can graph the points and see if they are linear.
- Enter the data from example 1 into L1 and L2
- Stat
- Edit
- Enter the data…if there is already data in your lists you can more the cursor to the very top (on L1) and press clear enter. This will clear the list.
- Turn Stat plot on
- Press 2nd y= (stat plot)
- Select 1
- Select on
- Type: first option, this is the scatter plot
- Graph the scatter plot
- Zoom
- Zoomstat – this changes the window to values that are best for your set of data, without us having to pick the best window

- Check by graphing the equation as well
- Put the equation into y1
- Press trace or graph
- The line should go through all of the points
- When you are done using the stat plot option go to stat plot and choose 4:plots off enter. This will shut off the statplots.
- To change your window back to standard –10-10 press zoom, zoom standard

- The Regression Line
- Also called the least-squares fit
- Approximate model for functions

- Uses of the regression line
- Finding slope…tells us how the data values are changing.
- Analyzing trends
- Predicting the future (not always accurate)
- Shows linear trend of the data

- Enter data into L1 and L2
- Plot the scatter plot
- Go to stat
- Calc
- LinReg(a + bx)
- Enter
- Enter
- a = slope, b = y-intercept
- Graph with the points to see how close it is.

- If the equation has a constant rate of change then it is a line.
- Linear functions are formulas for graphing straight lines.
- Slope intercept form: y = mx + b
- Standard form: ax + by = c, a and b are both integers, a>0

- The initial value is when x = 0, which happens to be the y-intercept (b)
- Use y = mx + b

- Initial value of 35, slope of ½
- A phone company charges a flat fee of $29.99 plus $0.05 a minute.

- A local school is going on a field trip. The cost is $130 for the bus and an additional $2 per child.
- Write a formula for the linear function that models the cost for n children.
- How much is it for 15 children to attend?

2.2

Equations of Lines

- Given point, (a, b), and slope, m, the equation can be found using the formula
y – b = m(x – a).

This is called the point-slope form of the line.

- Find the equation of the line passing through the given point with the given slope. Write your answer in point slope form.
- (6, 12), m = –1/3
- (1, -4), m = 1/3

- Find the equation of the line passing through the given points. Use the first point as (x1,y1) and write your answer in point slope form.
- (-2,3), (1,0)
- (-1,2), (-2,-3)

- Slope Intercept form of a line:
- y = mx + b
- m = slope
- b= y-intercept

- y = mx + b

- Find the equation of each line in point slope form and in slope-intercept form.
- (2,3) m = ½
- (-3, 5) m = 2
- (-8, 7) m = -3/2

- Horizontal Intercept- where the line crosses the x axis
- This can be found by letting y = 0

- Vertical Intercept- where the line crosses the y axis
- This can be found by letting x = 0.

- Locate the x- and y-intercepts on the following lines.
- -3x – 5y = 15
- (2/3)y – x = 1

- An equation of the horizontal line with y-intercept b is y = b.
- An equation of the vertical line with x-intercept k is x = k.

- Find the equation of the line satisfying the conditions:
- Vertical passing through (1.95, 10.7)
- Horizontal passing through (1.95, 10.7)

- Parallel lines have the same slope. (They are changing at the same rate)
- Slopes of perpendicular lines are negative reciprocals of one other.
- Ex: ½ and -2; 2/3 and -3/2; -5 and 1/5

- For each of the following pairs of lines, determine whether the lines are parallel, perpendicular or neither.
a. 3x + 2y = 4 and 6x + 4y = 9

b. 5x – 7y = 3 and 4x – 3y = 8

c. 5x – 7y = 15 and 15y - 21x = 7

d. ax = by = c and akx +aky = d, (a ≠ 0)

- 2x – 3y = 9, (-9, 7)
- 4x + 5y = 16, (-2, 3)

- 3x + 4y = 8, (7, 3)
- 2x – 8y = 10, (1, 0)

- Show that the points (1, 1), (3,4) and (4,-1) from the vertices of a right triangle.

- Interpolation
- Estimates values that are between two or more known data values.

- Extrapolation
- Estimates values that are not between two known data values.

- Page 101 #54

- Let x and y denote two quantities. Then y is directly proportional to x, or y varies directly with x, if there exists a nonzero number k such that y = kx.
- k is called the constant of proportionality or the constant of variation.

- Page 104 # 100

- Page 102 #80

- Page 103 #88

- Page 03 #90

- Page 104 #104

2.3

Linear Equations

- Page 118 #18
- Page 118 #20

- Page 118 #22
- Page 118 #24

- Page 118 #30
- Page 119 #36

- Page 119 #46

- Page 119 #60
- Page 119 #64

- Page 120 #80

- Page 121 #86

- Page 121 #88

- Page 122 #98

- Page 122 #100

2.4

Linear Inequalities

- A linear inequality in one variable is an inequality that cab be written in the form
ax + b >0 where a ≠ 0.

(The symbol > can be replaced by <, ≤, or ≥)

- Interval Notation
- Open interval ( )
- Half-open interval ( ], [ )
- Closed interval [ ]
- Infinite intervals

- Page 134 #4
- #6
- #8
- #10

- Follow the equation rules when solving inequalities.
- When you multiply or divide both sides by a negative flip the inequality sign.

- Page 134 #14
- Page 135 #18

- Page 135 #22
- Page 135 #28

- Page 135 #38
- Page 135 #40

- Page 135 #60

- Page 136 #70

- Page 136 #86

- Page 137 #88

- Page 137 #92

- Page 138 #98

2.5

Piecewise-Defined Functions

Page 152 #2

- Page 153 #6

- Page 153 #8

- Page 153 #12

- Greatest Integer Function
- [[x]] is the greatest integer less than or equal to x.
(Always round down.)

[[1.2]] = 1

[[1.9]] = 1

- [[x]] is the greatest integer less than or equal to x.

- Page 154 #24

- Page 154 #28

- Page 154 #38

- Solving Absolute Value Equations and Inequalities
- Break it into 2 parts
- Flip the second symbol and sign

- Page 154 #40
- Page 154 #42

- Page 155 #56

- Page 155 #60

- Page 155 #68
- Page 155 #74

- Page 155 #80

- Page 156 #100

- Page 156 #104