For items 21 - 23 determine whether each sequence is arithmetic. if the sequence is arithmetic, then

see below

Step-by-step explanation:

To be arithmetic we have to add the same term each time

1,1,2,3,5,8

1+1 =2  2+1 = 3  3+1 = 4  so it is not arithmetic

20,17,14,11,8,

Add -3

20+-3 =17   17+-3 = 14  14+-3 = 11   11+-3 = 8

This is an arithmetic sequence

The common difference is -3

The explicit formula is

an = a1+ d(n-1)  where d is the common difference and a1 is the first term

an = 20 -3( n-1)

The recursive formula is

an = an-1 + d  where an-1 is the previous term and d is the common difference

an = an-1  -3

3,7,11, 15

Add 4

3+4=7  7+4=11  11+4=15

This is an arithmetic sequence

The common difference is 4

The explicit formula is

an = a1+ d(n-1)  where d is the common difference and a1 is the first term

an = 3 +4( n-1)

The recursive formula is

an = an-1 + d  where an-1 is the previous term and d is the common difference

an = an-1  +4

took the test it's 94