Question

the number of tickets sold each day for an upcoming performance is given by n(x)=-0.4x^2+10.4x+14, where x is the number of days of the concert was first announced. when will the daily ticket sales peak and how many will be sold that day... i wrote the first question wrong

Answer 1

n'(x)=-0.8x+10.4 and n''(x)=-0.8 so whatever critical point is a maximum.
n'(x)=0 when x=13.
n(13)=81.6 or approximately 81 tickets will be sold on the 13th day. :D