The number of tickets sold each day for a performance is given by N(x)=-0.4x^2+8x+14, where x is 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?

Hmm. I get max tickets on day

-b/2a = 8/.8 = 10
N(10) = -40+80+14 = 54