The total cost in $ of manufacturing 'm' treadmills is given by the function c(m)=m^3-20m^2+500m+100. Whats the average cost?

The average cost is the total cost over the number of units.

You are given a function for total cost:

c(m) = m³ - 20m² + 500m + 100

So to get average cost, just divide it by m:

(m³ - 20m² + 500m + 100) / m

or

m² - 20m + 500 + (100/m)

Cost, c(m) = m^3-20m^2+500m+100
Average cost = c(m)/m = m^2 - 20m + 500 + 100/m