I got some same type of qns that i don't know how to solve.

Find:$\displaystyle \sum^{n}_{r=1} \frac{1}{(2n+3)(2n+1)}$

I found and checked the ans to be $\displaystyle \frac{1}{6} - \frac{1}{4n+1}$

Hence solve $\displaystyle \sum^{n}_{r=1} \frac{1}{4n^2 -1}$

And another similar one,find $\displaystyle \sum^{n}_{r=3} \frac{4-r}{r(r-1)(r-2)}$

hence find $\displaystyle \sum^{n}_{r=1} \frac{2-r}{r(r+1)(r+2)}$

I dont know how to do the hence part. Btw sorry about the summation. i cant figure out how to use latex properly

Thank you for ur time