1. A sequence is defined using this term-to-term rule,

${u}_{n+1}=k{u}_{n}+r$

where $k$ and $r$ are constants.

Given that ${u}_{2}=41$ , ${u}_{3}=206$ and ${u}_{4}=1031$, find the value of $k$ and the value of $r$.

$k$= ................

$r$ = .................