The adjacent table gives the number of worldwide Internet us

The adjacent table gives the number of worldwide Internet users, in millions. Complete parts (a) through (c) (a) Find the cubic function that is the best fit for the data, with y equal to the number of millions of users and x equal to the number of years from 1990 y = (Use integers or decimals for any numbers in the expression Round to three decimal places as needed.) (b) Use the model to predict the number of users in 2013. The number of users in 2013 will be approximately million (Round to the nearest whole number as needed.) (c) Compare the graphs of the data and the model to determine if the model is a good or poor fit for the data. Good Fit Poor Fit

Solution

xuru.org ----> regression tools ---> polynomial regression

At this step, change the degree to 3
for cubic regression

Enter the coordinates as :
(5,18)
(6,32)
(7,72)
(8,181)
(9,290)
(10,342)
(11,518)
(12,587)
(13,718)
(14,823)
(15,1011)
(16,1093)
(17,1231)

I get :

-0.409x^3 + 17.282x^2 - 115.174x + 198.879 ---> ANSWER

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b)
In 2013,
t = 2013 - 1990 = 23

So plug in 23....

-0.409(23)^3 + 17.282(23)^2 - 115.174(23) + 198.879

1716 -----> ANSWER

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c)
Good fit