Use the data in the table to model the population of the world in to 20th century by a cubic function. Then use your model to estimate the population in the year 1925.
Year Population (millions) 1900 1650 1910 1750 1920 1860 1930 2070 1940 2300 1950 2520 1960 3020 1970 3700 1980 4450 1990 5300 1996 5770
Using a graphing calculator to plot the points and do a cubic regression, I get the equation y=.00233x3 - 13.065x2 + 24463.108x - 15265793.873, which matches with the answer in the back of the book. But when I plug in 1925 for x into the equation, I get 32,352.933, which doesn't make since when looking at the table. The answer in the back of the book is 1922 million, which makes more sense because this is a suitable answer since it is between 1750 and 1860 (the values that correspond to years 1910 and 1920). I'm probably missing something very simple. How do I get 1922 million?