SOLUTION: At a price of $3.10 a gallon, the weekly demand for gas is 42 gallons. If the price rises to $3.25 a gallon, the demand drops to 39 gallons. Find the formula for quantity of gas

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: At a price of $3.10 a gallon, the weekly demand for gas is 42 gallons. If the price rises to $3.25 a gallon, the demand drops to 39 gallons. Find the formula for quantity of gas       Log On


   

Question 1037212: At a price of $3.10 a gallon, the weekly demand for gas is 42 gallons. If the price rises to $3.25 a gallon, the demand drops to 39 gallons. Find the formula for quantity of gas demanded in terms of “p”, the price per gallon, assuming the demand is linear.
Answer by Aldorozos(172) About Me  (Show Source):
You can put this solution on YOUR website!
Equation of a line when we have two points on the line: y-y1 = [(x2-x1)/(y2-y1]/(x-x1)
http://www.coolmath.com/algebra/08-lines/12-finding-equation-two-points-01

y-42 = [(3.25 -3.10)/39-42](x-3.1)
y-42 = .15/(-3) *(x-3.1)
y-43 = -.05(x-3.1)This is an equation of a line.