algebra
posted by Jack .
The number of tickets soldeach day for an upcoming performance of Handiel Messiah is given by N(x)=0.4x^2+9.6x+10,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.

Treat the equation as a parabola, find its vertex. When? what is the axis of symettry?