College Algebra 2
posted by sally .
The number of tickets sold each day for an upcoming performance of Handel's messiah is given by N (x) = 0.4x^2 + 11.2x + 12 where x is the number of days since the concert was first announced. when will daily tickets sales peak and how many tickets will be sold that day?

You must have copied something wrong.
N(x) as you have written it will increase with x. There will be no peak.
Are you sure there isn't supposed to be a minus sign in front of 0.4x^2?
Try making a graph to find the answer, once you have verified the correct equation. I recommend you round off N(x) to the nearest integer.