Mary lives 1 3/4 km from school. She rode her bike to school and back each day for 5 days. Which expression shows how to estimate the number of km she rode on her bike? A) ( 5+2 ) x 2
B) 5x (2+2)
C) (7+2) x2
D) 7x (2+2)

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)