Answers:
Hey there bud!
Just as a note, a linear sequence is when each number after another has a same added constant term.
i) Non-linear. +1 +2 +3. Not + same number
ii) Non-Linear. +(-8) +(-8) +(-8) +(-8) +(-9)
If you mistyped that, which I'm pretty sure you did, then I think it's a linear sequence for ii.
iii) Non-Linear. -3, -6, -9
iv) Linear. -2 -2 -2 -2 -2 etc.
