SOLUTION: This equation is a word problem for ticket sales in the form of a formula. The equation is -0.2x^2 + 12x + 11. I have changed the signs to begin with. a=.2x^2 b=-12 and c=-11, the

Question 340886: This equation is a word problem for ticket sales in the form of a formula. The equation is -0.2x^2 + 12x + 11. I have changed the signs to begin with. a=.2x^2 b=-12 and c=-11, the equation solver for the plotted points is -b+/- sqrt b^2 -4ac/2a is where I have started. I have come up with 135.2/.4 in this formula. Is this correct? To determine the last day of the ticket sales and the peak day or days for sales, is what I am having trouble with. Could you give me a step by step explanation of the the solutions, I have to have a visual aid to help me understand.
Answer by stanbon(57984) (Show Source):
You can put this solution on YOUR website!
This equation is a word problem for ticket sales in the form of a formula. The equation is -0.2x^2 + 12x + 11. I have changed the signs to begin with. a=.2x^2 b=-12 and c=-11, the equation solver for the plotted points is -b+/- sqrt b^2 -4ac/2a is where I have started. I have come up with 135.2/.4 in this formula. Is this correct? To determine the last day of the ticket sales and the peak day or days for sales,
---
sales = -0.2x^2+12x+11
a = -0.2 ; b = 12 ; c = 11
----
x = [-12 +- sqrt(144-4*-0.2*11)]/(2*-0.2)
---
x = [-12 +- sqrt(152.8)]/-0.4
--------
x = [-12 +- 12.36]/(-0.4)
---
x = (0.36/-0.4) or x = (-24.36/-0.4)
x = -0.9 or x = 60.9
----
Last day of ticket sales is day 60
Peak day for sales is day 30

=====================
Cheers,
Stan H.