The function is
.
Apply first derivative with respect to
.
Apply second derivative with respect to
.

The values of
is
.
Test for concavity in the intervals
and
, as shown in the below table.
| Intervals | \Test value | \ \
Sign of | \
Conclusion | \
![]() | \
![]() | \
\
| \
Concave upward | \
![]() | \
\
| \
![]() | \
Concave downward | \
The function is concave upward in the interval
.
Concave down in the interval
.
Concave upward in the interval
.
Concave down in the interval
.