Question

Write a recursive formula for the following arithmetic sequence.12, 5, -2, -9, ...an= 0=for n ≥ 2

Answer 1

We have the arithmetic sequence:

12, 5, -2, -9, ...

We first need to know which is the common difference between the terms, clearly, it is -7.

Now we just need to use the formula below:

`a_n=a_1+(n-1)d`

Where d is the common difference between the terms.

So we have:

`a_n=12+(n-1)*-7=-7n+19`

Then the correct answer is the recursive formula:

`a_1=12`

`a_n=a(n-1)-7`