PLEASE HELP I NEED U > I BEGG

Which of the following are accepted without proof in a logical system? check all that apply.

The position of a moving particle is given by the position function: f(t)=-9t-t^2-0.2t^3+0.1t^4 0 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)

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.