y
1
(
x
) =
x
2
,
y
2
(
x
) =
x
2
+
x
3
,
y
3
(
x
) =
x
2
+
x
3
+
x
4
, °
y
4
(
x
) =
x
2
+
x
3
+
x
4
+
x
5
.