Question

An=11+(n-1)(4) how do you write this in the recursive formula?

Answer 1

The answer is
$\begin{cases}A_1 = 11 \\ A_{n} = A_{n-1}+4\end{cases}$
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Explanation:
The first term is $A_1 = 11$. The next part of the rule, which says $A_{n} = A_{n-1}+4$ is the recursive part. To get the nth term, we add on 4 to the previous (n-1) term. For example, to get the fifth term, you add on 4 to the fourth term. Relying solely on this recursive definition means we need to find all of the previous terms (from 1 to n-1) in order to find a given nth term.