Three undefined terms in mathematics: I. Point
II. Line
III. Plane

The mathematical term parallel lines explicitly use the undefined term(s)

The mathematical term perpendicular lines explicitly use the undefined term(s)
.

The mathematical term line segment explicitly uses the undefined term(s)
.

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)