Question

An arithmetic sequence is defined by the recursive formuala t1=9,tn=tn-1-4 where n enand n>1 the seuence s

Answer 1

It's not clear what you're supposed to do, but I would guess that you're asked to find a certain term in the sequence.

Given


`\begin{cases}t_1=9\\t_n=t_(n-1)-4&\text{for }n>1\end{cases}`

you can do that by solving for
`t_n` explicitly.


`t_n=t_(n-1)-4=t_(n-2)-2*4=t_(n-3)-3*4=\cdots=t_1-(n-1)*4`

So the explicit formula for the
`n`th term is


`t_n=9-4(n-1)=13-4n`