Question

When I tried this problem, I got a_n=28-7(n-1) as an answer but it was marked as wrong so pls help me with it lol

Answer 1

We have the next sequence:

28,21,14,7....

We can find the common difference :

28

28-7= 21

21-7 = 14

14-7=7

Hence, the common difference is d=-7.

The recursive formula is given by:

`\begin{gathered} a_n=a_(n-1)+d \\ \text{Then:} \\ a_n=a_(n-1)-7 \end{gathered}`