Let f(x) = x / (x^2 + 11). Find (a) the intervals on which f is increasing,
(b) the intervals on which f is decreasing, (c) the open intervals
on which f is concave up, (d) the open intervals on which f is
concave down, and (e) the x-coordinates of all inflection points.
(a) f is increasing on the interval(s)
(b) f is decreasing on the interval(s)
(c) f is concave up on the open interval(s)
(d) f is concave down on the open interval(s)
(e) the x coordinate(s) of the points of inflection are