3. (a) [5 points] Find all the points on the graph of f(x) = x2 + 2x + 1 whose tangent line goes through the point (-1, -4). Hints: (i) Let (a, f(a)) be an unknown point on the graph of f(x) and find the slope of the line connecting (a, f(a)) to (-1, -4). (ii) Use the derivative to compute the slope of the tangent line to f(x) at the point I = a. (iii) Set these two slope equations equal to each other and solve for a. (b) [5 points] Let C(x) denote the cost function for producing x units of some product. Assuming x > 0, we can define the average cost function C(x) = (x) Show that the derivative of C(x) is equal to zero whenever C' (x) = C(x)