Question

This plz with working

Answer 1

`S_3=35`

Explanation:

Given:
`S_1=3\,,S_n=7(S_(n-1)-2)`

To find:
`S_3`

Solution:

First find
`S_2`

Put
`n=2` in
`S_n=7(S_(n-1)-2)`

`S_2=7(S_(2-1)-2)\\S_2=7(S_1-2)`

Put
`S_1=3`

`S_2=7(3-2)=7`

Now find
`S_3`

Put
`n=3` in
`S_n=7(S_(n-1)-2)`

`S_3=7(S_(3-1)-2)\\S_3=7(S_(2)-2)`

Put
`S_2=7`

`S_3=7[(7)-2]=7(5)=35`