A Cyclist is riding on a path whose elevation is modeled by the function f(x) = 0.08(16x-x^2) where x and f(x) are measured in miles. Find the rate of change of elecation when x=4. Would this be 0.64?

Question

A Cyclist is riding on a path whose elevation is modeled by the function f(x) = 0.08(16x-x^2) where x and f(x) are measured in miles. Find the rate of change of elecation when x=4. Would this be 0.64?
dx/dt would be 1.28 - 0.16x and then plug in four?

Steve · Answer

df/dx = .08(16-2x) at x=4, df/dx = .08*8 = .64 as you figured.