The signs of g′(x) and g′′(x) for a twice-differentiable function g are shown below.
Interval (−∞,−1)(−1,2)(2,∞)g′(x) \;–\; \;+\; \;+\;
g′′(x) \;–\; \;–\; \;+\;
On which interval is g decreasing and concave down?
a) (−1,2)
b) (−∞,2)
c) (−∞,−1)
d) (−1,∞)