The number of Americans who participate in aerobic exercise in thousands can be modeled by
E(a) -7.5a2+523.1a - 3312.3
where E(a) represents the number of people in thousands who participated in aerobic exercise at age a years old.
(a) Find the number of 25-year-old Americans who participate in aerobic exercise. (Round your answer to one decimal place.)
There are
x thousand 25-year-old Americans who participate in aerobic exercise.
(b) At what age(s) do 4 million Americans participate in aerobic exercise? (Hint: 4 million = 4000 thousand. Enter your answers from smallest to largest.)
About 4 million
-year-old Americans and 4 million
-year-old Americans participate in aerobic exercise.