Question 321698
you charge $1 per cup of lemonade you sell 60 cups.
 But when you raise your price to $1.50 you only sell 30 cups
 Write an equation for the number of cups you sell as a function of the price you charge.
 Denote "C" for number of cups, and "P" for the price you charge
:
the slope of the equation: m = {{{(y2-y1)/(x2-x1)}}}
Assign the given values as follows:
x1=1.00, y1=60
x2=1.50, y2=30
Find the slope
m = {{{(30-60)/(1.5-1)}}} = {{{(-30)/.5}}} = -60 is the slope
:
Use the point/slope formula: y - y1 - m(x - x1)
y - 60 = -60(x - 1)
y - 60 = -60x + 60
y = -60x + 60 + 60
y = -60x + 120
:
c = -60p + 120, is the equation