Answer:
see below
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