Question

Write a recursive formula for each sequence.19, 7, -5, -17, ...9, = 0n= for n ≥ 2an==5, 20, 80, 320, ...for n ≥ 2

Answer 1

First sequence:

$\begin{gathered} a_1=19 \\ a_n=a_1-12(n-1)=19-12n+1\Rightarrow a_n=20-12n \end{gathered}$

Second sequence:

$\begin{gathered} a_1=5 \\ a_n=a_1\cdot4^{n-1}\Rightarrow a_n=5\cdot4^{n-1} \end{gathered}$