Given :
When price is $2 dollars he sells 2400 units .
When price is $8 dollars he sells 600 units .
To Find :
If x represents the price of trucks and y the number of items sold, write an equation for the demand curve.
Solution :
Two points are given :
Now , slope is given by :
Now , the equation of line containing these two points and slope -300 is :
Therefore , equation for the demand curve is .
Hence , this is the required solution .