#### Answer

a) $f'(x)<0$ and $f''(x)<0$ for all $x$.
b) $f'(x)>0$ and $f''(x)>0$ for all $x$.

#### Work Step by Step

(a) The function is decreasing, so $f'(x)<0$, and the function is concave down, so $f''(x)<0$.
(b) For this function, it is increasing, so $f'(x)>0$, and it is concave up so $f''(x)>0$.