n
1
2
3
4
5
6
7
8
9
1
0
r
r
o
o
t
s
o
f
t
h
e
f
i
r
s
t
n
d
e
r
i
v
a
t
i
v
e
s
o
f
f
(
z
)
=
(
z
-
r
n
)
\)
,
(
z
+
i
)
(
z
-
i
)
.