(2n+3)! / (2n+4)!
1/(2n+4) = 1/(2(n+2))
\(\begin{array}{|rcll|} \hline (2n+4)! &=& (2n+3)!\cdot (2n+3+1) \\ &=& (2n+3)!\cdot (2n+4) \\\\ && \frac{(2n+3)!} { (2n+4)!}\\ &=& \frac{(2n+3)!} { (2n+3)!\cdot (2n+4) }\\ &=& \frac{1} { (2n+4) }\\ \hline \end{array}\)