Given the function, C(X), and the revenue function, R(x), find the number of x units that must be sold to break even.

Question

C(x)=5x+21

R(x)=-x^2+17x

Answer 1

5x + 21 = -x^2 + 17x

x^2 - 12x + 21 = 0

12 +or- sqrt( 144 - 4*21) / 2

12 +or- sqrt( 60) / 2

12 +or- 2*Sqrt(15) / 2

6 +or- sqrt(15) = 9.872+ or 3.872+