Find the value of the derivative (if it exists) at each indicated extremum. (if an answer does not exist, enter dne.)
f (x) = cosπx/2

Which fraction below is equivalent to 10/12?

Monthly water bills for a city have a mean of $108.43 and a standard deviation of $32.09. find the probability that a randomly selected bill will have an amount greater than $155, which the city believes might indicate that someone is wasting water. would a bill that size be considered unusual?

What are the solutions of the system? solve by graphing. y = -x^2 -6x - 7 y = 2