Question 87895
Equilibrium price is when the Demand is equal to the Supply.

{{{D = S }}}
{{{-200p+35000 = -p^2+400-20000 }}}
{{{p^2 - 200p + 54600 = 0 }}}
This very similar to {{{ax^2 + bx + c = 0 }}}
Now solve with {{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}