{
f
(
x
)
=
1
x
+
a
f
(
n
)
(
x
)
=
(
−
1
)
n
n
!
(
x
+
a
)
n
+
1
(1)
\left\{
{
f
(
x
)
=
x
n
f
n
(
x
)
=
n
!
(2)
\left\{
{
f
(
x
)
=
ln
x
f
n
(
x
)
=
(
−
1
)
n
−
1
(
n
−
1
)
!
x
n
(3)
\left\{
{
f
(
x
)
=
e
x
f
n
(
x
)
=
(
−
1
)
n
e
(
−
x
)
(4)
\left\{