Identify the exponential function for this graph. (Be sure to look at the scales on the x and yaxes.)
a. f(x)=4•(0.5)^x
b. f(x)=2•(0.25)^x
c. f(x)=2•(4)^x
d. f(x)=4•(2)^x

Lin is writing an equation to model the proportional relationship between y, the total cost in dollars of downloading videos from a website, and x, the number of videos downloaded. she knows that the total cost to download 3 videos was $12. her work to find the equation is shown below. joylin’s work step 1 k= 3/12= 0.25 step 2 y= 0.25x where did joylin make her first error?