57. If f and g are both decreasing on (a,b) then fg must be decreasing on (a,b) (section 4.2) 58. If the graph of f is concave upward on (a,b), then the graph of Of is concave downward on (a,b) 59. If the second derivative of f exists on (a,b) and the graph of f has an inflection point at (c, f(c)) where a c b , then f"(c) DO 60. If c is a critical number of f where a c band f"(c) 20 on (a,b), then f has a relative minimum at x Oc