Question 430491
  <pre><font face = "Tohoma" size = 4 color = "indigo"><b> 
Hi
 N(x)=-0.6x^2+18x+12    |represents a parabola opening downward
 N(x)=-0.6[(x-15)^2 - 225)+12    |completing the square to find the vertex
 N(x)=-0.6(x-15)^2 +135 + 12
 N(x)=-0.6(x-15)^2 + 147   Sales will peak on the 15th day with 147 tickets sold

{{{drawing(300,300,   -200,200,-200,200, blue(line(15,200,15,-200))  , grid(1),
circle(15, 147,1.0),
graph( 300, 300, -200,200,-200,200,0,-0.6x^2+18x+12 ))}}}