An engineer has designed a valve that will regulate water pressure on an automobile engine. The valve was tested on 280 engines and the mean
pressure was 7.5 pounds/square inch (psi). Assume the population variance is 0.81. If the valve was designed to produce a mean pressure of 7.6 psi.
is there sufficient evidence at the 0.1 level that the valve does not perform to the specifications?

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)