There are 4 blue marbles, 3 red marbles, 3 yellow marbles, and 2 green marbles. What is probability that Ms. Bennetti picks a blue marble, places it in her bag, and then picks a second blue marble?
Enter your answer as a fraction in simplest form:

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)