rate of change = slope
[tex]slope = \frac{y_{2}- y_{1} }{x_{2}- x_{1} } [/tex]
we pick any two x values so lets pick 3 and 4,
[tex]3 = x_{1} [/tex]
[tex]4 = x_{2} [/tex]
and our y values for these x's are 75 and 100
[tex]75 = y_{1} [/tex]
[tex]100 = y_{2} [/tex]
so we plug it into our equation
[tex] \frac{100-75}{4-3} [/tex]
solve
[tex] \frac{100-75}{4-3} = \frac{25}{1}=25 [/tex]
and our rate of change is 25. The 25 tells us that for each additional day, the price increases by $25
