SOLUTION: I submitted this earlier, but have not seen this answered yet. I got $58.58 and $341.42 but cannot get the numbers to check. I think I am doing the demand problem incorrectly....

Question 42812: I submitted this earlier, but have not seen this answered yet. I got $58.58 and $341.42 but cannot get the numbers to check. I think I am doing the demand problem incorrectly....HELP.
The demand equation for a certain type of printer is given by
D= -200p + 35,000
The supply equation is predicted to be
S= -p2 + 400p - 20,000
Find the equilibrium price.

-200p + 35,000 = -p2 + 400p - 20,000
-p2 - 400p - 20,000 = 0
a = 1 b = -400 c = 20,000
D = - 200(58.58) + 35,000 = -11,716 + 35,000
= 23,284
S= -(58.58)2 + 400(58.58) - 20,000
D = - 200(341.42) + 35,000 = -68284 + 35,000
= 33284
S= -(341.42)2 + 400(341.42) - 20,000

Answer by psbhowmick(878) (Show Source): You can put this solution on YOUR website!
Price will be in equilibrium when demand is equal to supply.

So for equilibrium price, D = S i.e.
or .

To find the equilibrium price we have to solve the above quadratic equation
.
Applying quadratic formula,

or
or
Either p = 487.08 or p = 112.92

Hence $487.08 and $112.92 are the two values of equilibrium prices.
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