Please help and explain ASAP

Complete the standard form of the equation that represents the quadratic relationship displayed above, where a, b, and c are rational numbers.

Select a graph that have an equation with a < 0

The first-serve percentage of a tennis player in a match is normally distributed with a standard deviation of 4.3%. if a sample of 15 random matches of the player is taken, the mean first-serve percentage is found to be 26.4%. what is the margin of error of the sample mean? a. 0.086% b. 0.533% c. 1.11% d. 2.22%