Question 451608
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Hi
Using the vertex form of a parabola, {{{y=a(x-h)^2 +k}}} where(h,k) is the vertex
Tickets = -0.2x^2+12x+11  |Completing the square to find the vertex 
        = -.2[(x -30)^2  - 900] + 11
        = -.2(x-30)^2 + 180 + 11
        = -.2(x-30)^2 + 191  Descriptive of a parabola opening downward V(30,191)
Ticket sales peak when x = 30 at 191ticket sales and decline after that.