Question 50921
D= -200p + 35,000 
The supply equation is predicted to be 
S = p^2 + 400 p - 20,000 
Find the equilibrium price.
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I guess you have equilibrium when S = D, so:
-200p+35000=p^2+400p-20000
p^2+600p-55000=0
p=[-600+-sqrt(600^2-4(-55000)]/2
p=80.79 or -380.79
I think only the positive value applies.
Cheers,
Stan H.