PLEASE ITS DUE TONIGHT. All help is really appreciated.

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)

Agrasshopper weighs 0.89 grams. express the grasshopper’s weight in scientific notation.

Solve the system of equations. x=-2y+1 and x+2y=9. show work