Two buyers have demand functions q₁ = 20 − 2P and q₂ = 30 − 3P. What is the market demand function?

Explanation

1. 01

   Add the quantities at each price: (20 − 2P) + (30 − 3P) = 50 − 5P.

2. 02

   Both buyers demand something only up to P = 10, so the sum holds for prices from 0 to 10.