Pre-Algebra help needed: Arithmetic, Finding the first term of each sequence

Hey everyone I'm doing my Pre-Algebra homework and I am trying to figure out what these mean?

Find the first five terms of each sequence defined by the given rule.
21. An = N-1/N+1 22. an = n(n - 1) - 2n 23. an = 3n/ n+1

I have no idea what these mean so if anyone could help me please answer. Btw this "/" = 'Over' meaning it's written as a fraction.

It's a sequence. Depending on whether the sequence starts at N = 0, or N =1, you substitute the value for N.

#21
Assuming the first term is A_0:

A_0 = (0 - 1) / (0 + 1) = -1 / 1 = -1

The second term would be A_1:

A_1 = (1 - 1) / (1 + 1) = 0 / 2 = 0

You would repeat this pattern until you get the first five terms.

If you understand this, then #22 and #23 will be very easy as they follow the same logic.

Hope this helps!!