I have no clue how to solve these. Someone please help...

1) How to determine the convergence or divergence of the following series:

a) lim of ((-1)^(n+1) *n)/ (2n-1) when n=1

b) lim of ((-1)^(n+1) *n^2)/ (n^2 + 5) when n=1

c) lim of (2(-1)^(n+1))/ (e^n + e^-n)= lim of ((-1)^(n+1) * sech n) when n=1

2) Determine whether the following series converges conditionally or absolutely, or diverges.

a) lim of ((-1)^(n+1))/ (n+1) when n=1

b) lim of ((-1)^n * e^(-n^2)) when n=0

c) lim of ((-1)^(n+1) * arctan n) when n=1

3) Using the alternating Series Remainder Theorem, determine the number of terms required to approximate the sum of the following series with an error of less than 0.001.

a) lim of ((-1)^(n+1)) / (n^2) when n=1