Consider the following.f(x) = (x2 + 4x + 4)(x − 4)(a) Find the derivative of the function, and check your work by graphing both your calculated derivative and the numerical derivative of the function.f '(x) =(b) Use your graph of the derivative to find points where the original function has horizontal tangent lines. (Enter your answers as a comma-separated list.)x =(c) Use a graphing calculator to graph the function and indicate the points found in part (b) on the graph.

Consider the following.
f(x) = (x2 + 4x + 4)(x − 4)
(a) Find the derivative of the function, and check your work by graphing both your calculated derivative and the numerical derivative of the function.
f '(x) =

(b) Use your graph of the derivative to find points where the original function has horizontal tangent lines. (Enter your answers as a comma-separated list.)
x =

(c) Use a graphing calculator to graph the function and indicate the points found in part (b) on the graph.