See Problem 4.

Use your models from Exercises 16-19 to make predictions.

20. Estimate total U.S. federal spending for 1990 and 2010.
21. Estimate the average annual growth rate of the world population for 1950, 1988, and 2010.
22. Estimate the average sale price of homes sold in the United States for 1985, 1999, and 2020.
23. Estimate the number of barrels of crude oil and petroleum supplied per day for January, March, and October of 2008.

B Apply

Find a cubic and a quartic model for each set of values. Explain why one models the data better.

24. x	− 2 negative 2	− 1 negative 1	0	2	3
    y	− 25 negative 25	− 4 negative 4	3	23	40

25. x	− 2 negative 2	− 1 negative 1	0	1	2
    y	− 65 negative 65	− 14 negative 14	− 4 negative 4	2	90

Find a polynomial function whose graph passes through the points.

26. ( − 14 , 14 ) , ( − 10 , 0 ) , ( 0 , − 1 ) , ( 8 , 0 ) ,  and  ( 12 , 4 ) open negative 14 comma 14 close comma open negative 10 comma 0 close comma open 0 comma negative 1 close comma open 8 comma 0 close comma , and , open 12 comma 4 close
27. ( − 3 , − 50 ) , ( − 2 , − 4 ) , ( − 1 , 10 ) , ( 0 , 7 ) ,  and  ( 2 , − 23 ) open negative 3 comma negative 50 close comma open negative 2 comma negative 4 close comma open negative 1 comma 10 close comma open 0 comma 7 close comma , and , open 2 comma negative 23 close

28. Think About a Plan The table below shows the amount of carbon dioxide in the Earth's atmosphere for selected years. Predict the amount of carbon dioxide in the Earth's atmosphere in 2022. How confident are you in your prediction?

    Year	CO  2 cap ccap o sub 2  in atmosphere (ppm)
    1968	324.14
    1983	343.91
    1998	367.68
    2003	376.68
    2008	385.60

    SOURCE: The Weather Channel

    • How can you plot the data? (Hint: Let x equal the years after 1900.)
    • What polynomial model should you use?

Find a cubic model for each set of values. Then use the regression coefficient of each model to determine whether the model is a good fit.

29. ( − 5 , − 60 ) , ( − 1 , − 5 ) , ( 0 , 0 . 5 ) , ( 1 , 8 ) , ( 5 , 17 ) , ( 10 , 32 ) open negative 5 comma negative 60 close comma open negative 1 comma negative 5 close comma open 0 comma 0 . 5 close comma open 1 comma 8 close comma open 5 comma 17 close comma open 10 comma 32 close
30. ( 8 , − 101 ) , ( − 1 , 10 ) , ( − 8 , 47 ) , ( − 10 , 59 ) open 8 comma negative 101 close comma open negative 1 comma 10 close comma open negative 8 comma 47 close comma open negative 10 comma 59 close

31. Air Travel The table shows the percent of on-time flights for selected years. Find a polynomial function to model the data. Use 1998 as Year 0.

    Year	1998	2000	2002	2004	2006
    On-time Flights (%)	77.20	72.59	82.14	78.08	75.45

    SOURCE: U.S. Bureau of Transportation Statistics

32. Writing Explain two ways to find a polynomial function to model a given set of data.

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