Help with Quadratics/Arithmetic Sequences

I'm not even sure if this is considered algebra to be honest.. but I'm guessing it is. I'm missing the same notes as some of my friends of course so I'm completely lost as to what to do for a few of these...

If I were to calculate the formula of this arithmetic sequence:

{-1, -3, -5, -7,...}

d1 is 2 right, and t1 (term one) is -1 so the formula would be, uhh, tn=t1+d1(n-1), or tn=-1+2(n-1) or tn=-1+2n-2... is that right?

The second one is if tn=-2n^2-3, find the first 5 terms. The first term is -2 right? but what do I do after that?

The third one... if tn=n^2-11, find which term has a value of 89... I think I go 89=n^2-11 but I'm still confused and not sure if that's right ?

Also, the hardest one that completely confuses me is Determine the equation of this quadratic sequence {3, 4, -1, -12, -29,...} Any advice on how to get that started?

Some help in working out these problems (and therefore problems similar to these) would be greatly appreciated