1] both arithmetic and geometric
d = 0, r = 1
2] arithmetic
d = 20
3] geometric
r = –2
4] geometric
r = 3
5] arithmetic
d = 1/15
6] arithmetic
d = –5
7] geometric
r = 0.6
8] geometric
r = 5
9] arithmetic
d = b
10] geometric
r = √2
11] geometric
r = x
12] arithmetic
d = 40
13] geometric
r = 9
