Please show all work. Write down the first four terms of each series.

a$){\displaystyle \underset{n=1}{\overset{}{}}}\frac{n}{2}$

b$){\displaystyle \underset{n=1}{\overset{}{}}}\frac{n}{(n1{)}^2}$

c$){\displaystyle \underset{n=0}{\overset{}{}}}\frac{n}{(n1{)}^2}$

d$){\displaystyle \underset{n=2}{\overset{}{}}}(-1{)}^n{n}^2$