SOLUTION: Demand: p=840-12q Supply=7q^2+2q Find the equilibrium price and quantity.

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Question 953448: Demand: p=840-12q Supply=7q^2+2q
Find the equilibrium price and quantity.
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!
equilibrium: the price and quantity that correspond to the point where supply and demand intersect (where Demand= Supply)
Demand: p=840-12q Supply=7q%5E2%2B2q
7q%5E2%2B2q=840-12q
7q%5E2%2B2q-840%2B12q=0
7q%5E2%2B14q-840=0
7q%5E2%2F7%2B14q%2F7-840%2F7=0
q%5E2%2B2q-120=0
q%5E2%2B12q-10q-120=0
%28q%5E2%2B12q%29-%2810q%2B120%29=0
q%28q%2B12%29-10%28q%2B12%29=0
%28q-10%29%28q%2B12%29+=+0
solutions:
if %28q-10%29+=+0=>q=10
if %28q%2B12%29+=+0=>q=-12...disregard this solution, the quantity cannot be negative
so, your solution is:q=10-----quantity
now find p
p=840-12q
p=840-12%2A10
p=840-120
p=720--------price
intersection point is at (q,p)=(10,720)