Question

The recursive rule for a sequence is an=an-1+7, where a1=15.What is the explict rule for this sequence

Answer 1

well, the recursive rule of aₙ = aₙ₊₁ + 7, where a₁ = 15, is simply saying that

we start of at 15, and the next term is obtained by simply adding 7, and so on.

well, that's the recursive rule.

so then let's use that common difference and first term for the explicit rule.

$\bf n^{th}\textit{ term of an arithmetic sequence} \\\\ a_n=a_1+(n-1)d\qquad \begin{cases} a_n=n^{th}\ term\\ n=\textit{term position}\\ a_1=\textit{first term}\\ d=\textit{common difference}\\ \cline{1-1} a_1=15\\ d=7 \end{cases} \\\\\\ a_n=15+(n-1)7\implies a_n=15+7n-7\implies a_n=7n+8$