Use a graphing calculator to find the intervals on which the function is increasing or decreasing. Consider the entire set of real numbers if no domain is given.
(a) f(x) = 8x / x2 + 1
(b) f(x) = -4 / x2 + 1
(c) f(x) = x√4 - x2, for -2 ≤ x ≤ 2
(d) f(x) = -0.8x√9 - x2, for -3 ≤ x ≤ 3