Chapter 4.1, Problem 1QCE

(a) A function $f$ is increasing on $\left(a,b\right)$ if $\text{\_\_\_\_\_\_\_}$ whenever $a<x_1<x_2<b.$

(b) A function $f$ is decreasing on $\left(a,b\right)$ if $\text{\_\_\_\_\_\_\_}$ whenever $a<x_1<x_2<b.$

(c) A function $f$ is concave up on $\left(a,b\right)$ if $f^{\prime }$ is $\text{\_\_\_\_\_\_\_}$ on $\left(a,b\right)$ .

(d) If $f^{″}\left(a\right)$ exists and $f$ has an inflection point at $x=a,$ then $f^{″}\left(a\right)\text{\_\_\_\_\_\_\_}$ .