The value of a cellular phone depreciates at a rate of 13% every month. If a new phone costs $300, which expressions model the value of the phone, after t years? 300(0. 87)/12 and 300(0. 1880)t
300(0. 87)t/12 and 300(0. 9885)t 300(0. 87)124 and 300(0. 1880)t
300(0. 87) 12 and 300(0. 9885)t

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)