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put this solution on YOUR website! -0.6x2 + 12x + 11
a. Does the graph of this equation open up or down? How did you determine this? (5pts)
DOWN - because the coefficient of the highest power term is negative.
How did you determine this?
.
B . Number of ticket sales goes down to zero.
c. c. Use the quadratic equation to determine the last day that tickets will be sold. (Note: Write your answer in terms of the number of days after ticket sales begin.)
Solve E(x) = 0 for "x>0".
E(x) = -0.2 X^2 + 12 x + 11
Find the roots of the equation by quadratic formula
-b/2a= 30
a= -0.2 b= 12 c= 11
b^2-4ac= 144 - 8.8
b^2-4ac= 152.8
= 12.36
x1=( -12 + 12.36 )/ -0.4
x1= -0.9 - 8/9
x2=( -12 -12.36 ) / -0.4
x2= 60.9 60 8/9
Take the positive solution - The sale goes down to 0 on the day 61
The x co-ordinate of the parabola is -b/2a = 30
The peak will occur after about 30 days
Plug value of x co-ordinate of vertex in the equation
y= -180 + 360 + 11
y= 191
191 Tickets will be sold when the sale reaches the peak.
The x co-ordinate of the parabola is -b/2a
plug the vakue of x in the equation to get the y co-ordinate of the vertex. Vertex ( 30 , 191 )
