6)
\Step 1:
\ The function is .
Differentiate on each side with respect to
.
Find the critical points.
\Since is a polynomial it is continuous at all the point.
Thus, the critical points exist when .
Equate to zero.
,
and
.
The critical points are ,
and
.
Substitute in
.
Substitute in
.
Substitute in
.
The critical points are and
.
The test intervals are ,
,
and
.
Interval | \Test Value | \Sign of ![]() | \
Conclusion | \
![]() | \
![]() | \
\
| \
Decreasing | \
![]() | \
![]() | \
\
| \
Increasing | \
![]() | \
![]() | \
\
| \
Decreasing | \
![]() | \
![]() | \
\
| \
Increasing | \
The function is increasing on the intervals and
.
The function is decreasing on the interval and
.
Step 2:
\.
Differentiate on each side with respect to
.
Find the inflection points.
\Equate to zero.
The inflection points are at .
Substitute in
.
Substitute in
.
Inflection points are and
.
The test intervals are ,
and
.
\
Interval \ | \
Test Value | \Sign of ![]() | \
Concavity | \
![]() | \
![]() | \
![]() | \
Up | \
![]() | \
![]() | \
![]() | \
Down | \
![]() | \
![]() | \
![]() | \
\
Up \ | \
The graph is concave up on the interval and
.
The graph is concave down on the interval .
The inflection point is .
Step 3:
\Graph the function :
Graph :
\1). Draw a coordinate plane.
\2). Plot the inflection points and critical points.
\3). Connect the plotted points.
\Solution: \ \
\The function is increasing on the intervals and
.
The function is decreasing on the intervals and
. \ \
The graph is concave up on the interval and
.
The graph is concave down on the interval .
\ \
\Graph of the function :
\
.