We want to write the recursive formula for the arithmetic sequence
We know that it is in the form
We know the first term of the sequence which is 9 so a1= 9
We need to find d, which is the common difference
Taking the second term and subtracting the first term
2 - 9 = -7
The common difference is -7
Checking
2+-7 = -5 -5-7 = -12 -12 -7 = -19
These are correct so our common difference is correct
an = an-1 -7
Answer: