college
posted by Joanne .
how can i solve this problem? The number of tickets sold each day for a upcoming peformance of Handel's Messiah is given by N(x)=0.4x^2+8x+11, where x us the number of days since the concert was first announced. When will daily ticket sales peak and how many tickets will be sold that day.

Your School Subject is Math, not "college."

since you labeled it "college" I will assume you know Calculus.
N(x)=0.4x^2+8x+11
N'(x) = .8x + 8
= 0 for a max/min of N
.8x + 8 = 0
x will be a negative, so your problem makes no sense.
your function is an upwards parabola so it has a minimum, not a maximum.
perhaps you have a typo and the first term is .8x^2
then the above result becomes
.8x + 8 = 0
x = 10
and N(10) = .8(100) + 80 + 11
= 11
11 tickets sold ????
There are more people singing Hallelujah. 
Apart from the subject, that equation isn't going to peak for x > 0. I think you may have an error in the question.