Answer
(a) $f'(x) \gt 0$ for all $x$, so the graph is increasing.
$f''(x) \lt 0$ for all $x$, so the graph is concave down.
(b) $f'(x) \lt 0$ for all $x$, so the graph is decreasing.
$f''(x) \gt 0$ for all $x$, so the graph is concave up.

Work Step by Step
(a) $f'(x) \gt 0$ for all $x$, so the graph is increasing.
$f''(x) \lt 0$ for all $x$, so the graph is concave down.
(b) $f'(x) \lt 0$ for all $x$, so the graph is decreasing.
$f''(x) \gt 0$ for all $x$, so the graph is concave up.
We can see the graphs below:
