America is getting older. The graph shows the projected elderly U.S. population for ages 6...

America is getting older. The graph shows the projected elderly U.S. population for ages 65–84 and for ages 85 and older.

The formula models the projected number of elderly Americans ages 65–84, E, in millions, xyears after 2010.

a. Use the formula to find the projected increase in the number of Americans ages 65–84, in millions, from 2020 to 2050. Express this difference in simplified radical form.

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b. Use a calculator and write your answer in part (a) to the nearest tenth. Does this rounded decimal overestimate or underestimate the difference in the projected data shown by the bar graph on the previous page? By how much?