A certain drug is administered once a day. The concentration of the drug in the patient's bloodstream increases rapidly at first, but each successive dose has less effect than the preceding one. The total amount of the drug (in mg) in the bloodstream after the first dose is 42 mg. The amount after the second dose is 10.5 mg. The amount after the third dose is 2.625 mg. Write an explicit formula to represent this scenario. If the answer has 42 then it has a number and ^n-1 and if it's 30 then just regular + #.

This is so harddd! solve. 1 + 1 = solve 4 + 4 = solve 3 x 3

Ineed me i stuck and i don’t want to get it wrong

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)