and 
in the interval,
Summary
Increasing and Decreasing Functions: Let f be a function defined on
some interval. Then for any two numbers and in the interval,
f is increasing on the interval if
f is decreasing on the interval if
The derivative will indicate where functions are increasing or decreasing:
for each x on an interval, f is increasing on the
interval;
for each x on an interval, f is decreasing on the
interval;
for each x on an interval, f is constant on the
interval.
Critical numbers: those numbers c in the domain of f for which
or 
doesn't exist. A critical point is a point whose
coordinates are (c,f(c)).
Examples: