2.4 using linear models - poudre school districtstaffweb.psdschools.org/kemotich/mrs_motichka... ·...
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2.4 Using Linear Models
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24 Using Linear Models
Objective: To write linear equations that model real world dataTo make predictions from linear models
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Check Skills You'll Need
1) (0.2, 9) and (3.4, 7.3)
2) (10, 17) and (11.5, 13.5)
Find the change in x and the change in y between each pair of points.
Evaluate each function for the given values.
3) f(x) = x 2 for x = 3, 0, 34 1
2
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Modeling Real World DataYou can write linear equations to model realworld problems.
Example: Transportation
Jacksonville, Florida has an elevation of 12 ft. above sea level. A hotair balloon taking off from Jacksonville rises 50 ft/min. Write an equation to model the balloon's elevation as a function of time. Graph the equation. Interpret the intercept at which the graph intersects the vertical axis.
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Jacksonville, Florida has an elevation of 12 ft. above sea level. A hotair balloon taking off from Jacksonville rises 50 ft/min. Write an equation to model the balloon's elevation as a function of time. Graph the equation. Interpret the intercept at which the graph intersects the vertical axis.
Relate: balloon's elevation = (rate)(time) + starting elevation
Define: Let h = the balloon's elevationLet t = time (in minutes) since the hotair balloon lifted off
Write: h = (50)(t) + 12h = 50t + 12
The hintercept is (0, 12).
The tcoordinate, 0, represents the time at the start of the trip.
The hcoordinate, 12, represents the elevation of the balloon at the start of the trip.
h
t
(0, 12).30
20
2 4 6
10
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A spring has a length of 8 cm when a 20g mass hangs at the bottom end. Each additional gram stretches the spring another 0.15 cm. Write an equation to model the length y of the spring as a function of the mass x of the attached weight.
Step 1: Identify the data points (20, 8) and (21, 8.15) as (x1, y1) and (x2, y2).
Step 2: Find the slope of the line.
Step 3: Use one of the points and the pointslope form towrite an equation for the line.
y = 0.15x + 5
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Using the previous equation, what mass could be needed to stretch the spring to a length of 9.5 cm?
y = 0.15x + 5
9.5 = 0.15x + 5
4.5 = 0.15x
30 = x
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A scatter plot is a graph that relates two different sets of data by plotting the data as ordered pairs.
Strong,negative No
A trend line is a line that approximates the relationship between the data sets of a scatter plot. You can use a trend line to make predictions.
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A woman is considering buying a 1999 car. She researches prices for various years of the same model car and records the data in a table.
Model Year 2000 2001 2002 2003 2004Prices $5784 $6810 $8237 $9660 $10,948j
$5435 $6207 $7751 $9127 $10,455
Let x represent model year (in years since 1999)Let y represent the price of the car
Draw a scatter plot
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Model Year 2000 2001 2002 2003 2004Prices $5784 $6810 $8237 $9660 $10,948j
$5435 $6207 $7751 $9127 $10,455
years (since 1999)
Price (in thousands)
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2 4 6 8
8
6
4
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Model Year 2000 2001 2002 2003 2004Prices $5784 $6810 $8237 $9660 $10,948j
$5435 $6207 $7751 $9127 $10,455
years (since 1999)
Price (in thousands)
Draw a trend line
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2 4 6 8
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Model Year 2000 2001 2002 2003 2004Prices $5784 $6810 $8237 $9660 $10,948j
$5435 $6207 $7751 $9127 $10,455
years (since 1999)
Price (in thousands)
Write the equation of the line
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If the car's asking price is $4,200, is this price reasonable?
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HomeworkHomeworkPage 81#'s: 1 11 odd, 12, 13
2.1 ‐ 2.3 Quiz MONDAY!!!!