ECON 11A Study Guide - Midterm Guide: Root Mean Square, 4X
Document Summary
Review questions 7 solutions ams 11a: denote by x the vertical dimension and by y the horizontal dimension of farmer. C(x, y ) = 8 (4x) + 12 (2x + 2y ) = 56x + 24y. Since xy = 4800, we can substitute y = 4800/x into the expression above to obtain the cost as a function of x alone: We want to nd the absolute minimum of this function on the interval (0, ) (since lengths must be positive). (a) critical points: dc dx. X 2 = 0 x = 120 . So there is only one critical point in (0, ): x0 = D2c dx 2: 5079. 84 is a relative min- 7 is the only critical point in (0, ), this imum value, and since x = 120/ is the absolute minimum cost. This minimum is attained when x = x . 45. 356 and y = 4800/x 105. 83, (so the gure above is not to scale).
