Question 472475
  <pre><font face = "Tohoma" size = 4 color = "indigo"><b> 
Hi,
Note:the vertex form of a parabola, {{{y=a(x-h)^2 +k}}} where(h,k) is the vertex
N(x)= -0.4x^2+12x+11
N(x)=-0.4[x^2 -30x]+11
N(x)=-0.4[(x-15)^2 -225]+11
N(x)=-0.4[(x-15)^2 -225]+11
N(x)=-0.4(x-15)^2 +101  V(15,101) a = -.4 a<0, Parabola opens downward
 V(15,101)is the Maximum Point. ticket sales peak on the 15th day with 101 sold
{{{drawing(300,300,   -50,50,-110,110,  grid(1),
circle(15, 101,1.3),
graph( 300, 300,-50,50,-110,110,0,-0.4x^2+12x+11
))}}}