On a coordinate plane, a line goes through points (1, 4) and (2, 8). Use the graph to find the relationship between the two variables. Select all that apply. The two variables are books and months. The two variables are 4 and 8. Books is the independent variable, and months is the dependent variable. Months is the independent variable, and books is the dependent variable. The relationship is y = 4x. The relationship is x = 4y.

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)