The function is .
Differentiate with respect to .
Again differentiate with respect to .
To find the intervals of increase and decrease, set .
cannot be equated to zero.
Therefore intervals are and
Consider a test point from the interval .
Let in
.
then
is decreasing in the interval
.
Consider a test point from the interval
Let in
.
then
is increasing in the interval
.
Therefore,
\ is decreasing in the interval
and increasing in the interval
.
To find the inflection points, set .
cannot be equated to zero.
Substitute in
Inflection point is .
The test intervals are and
.
Interval Test Value Sign of f(x) Conclusion
\
Concave upward
Concave downward
(a) is decreasing in the interval
and increasing in the interval
.
(b) Inflection point is .
(c) is concave up in the interval
and concave down in the interval
.