Determine which of these sequences is an arithmetic sequence. Then determine the explicit formula that would be used to define the nth term in the sequence.

6)

34, 43, 52, 61, ...

43-34 = 9; 52-43 = 9; 61-52 = 9

The difference between one term and the next is a constant so it is arithmetic sequence

first term:  a = 34

difference:  d = 9

so the formula:

7)

10, 6, 2, -2, ...

6-10 = -4; 2-6 = -4; -2-2 = -4

The difference between one term and the next is a constant so it is arithmetic sequence

first term:  a = 10

difference:  d = -4

so the formula:

8)

-3, -10, -17, -24, ...

-10-(-3) = -7; -17-(-10) = -7; -24-(-17) = -7

The difference between one term and the next is a constant so it is arithmetic sequence

first term:  a = -3

difference:  d = -7

so the formula:

9)

7, 8.5, 10, 11.5, ...

8.5-7 = 1.5; 10-8.5 = 1.5; 11.5-10 = 1.5

The difference between one term and the next is a constant so it is arithmetic sequence

first term:  a = 7

difference:  d = 1.5

so the formula:

10)

30, 22¹/₂, 15, 7¹/₂, ...

22¹/₂-30 = -7¹/₂;   15-22¹/₂ = -7¹/₂;   7¹/₂-15 = -7¹/₂

The difference between one term and the next is a constant so it is arithmetic sequence

first term:  a = 30

difference:  d = -7¹/₂

so the formula:

d

gimmee one of those gold crowns!

~coco

a. is correct