Section 6.1 Graphs and Their Representations
501
16.
5
1
2
3
4
(a)
a 2
a 6
a 3 a 4
a 9
a 8
a 1
a 7
e 1
e 3
e 6
e 7
d
c
a
b
e
e 2
e 4
e 5
e 8
e 9
(b)
a 5
17.
a
b
e
d
c
1
2
5
4
3
(b)
(a)
18.
1
4
2
3
6
5
(a)
a
b
c
f
e
d
(b)
19.
(a)
1
3
2
6
5
4
(b)
a
f
c
d
b
e