Having problems finding y in simplest form

Use the inverse of the function y=x^2-18x to find the unknown value [tex]y = \sqrt{bx + c \: + d} [/tex]

Margie is practicing for an upcoming tennis tournament. her first serve is good 20 out of 30 times on average. margie wants to know the estimated probability that her first serve will be good at least four of the next six times she serves. how could she design a simulation for this scenario?

Use a standard normal table to determine the probability. give your answer as a decimal to four decimal places. −1.5< < 1.5)