The function f(x) = -(x - 20)(x - 100) represents a company's monthly profit as a function of x, the number of purchase
orders received. Which number of purchase orders will generate the greatest profit?
圖6
20
O 60
O 80
o 100
and

The position of a moving particle is given by the position function: f(t)=-9t-t^2-0.2t^3+0.1t^4 a. at what time does the particle reverse direction? b. when is the displacement positive? (round one decimal place and answer in interval notation) c. when is the displacement negative? (round one decimal place and answer in interval notation) d. when is the particle’s acceleration positive? (round one decimal place and answer in interval notation) e. when is the particle’s acceleration negative? (round one decimal place and answer in interval notation)