What is the difference between explicit and recursive forms of sequences?

The parabola x= √y-9 opens: a.)up b.)down c.)right d.)left

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)

1) you deposit $2,500 in an account that earns 4% simple interest. how much do you earn in eight years?