回復 1# Exponential 的帖子
\(\begin{align}
& n{{a}_{n+1}}=\left( n+2 \right){{a}_{n}}+4n \\
& n\left[ {{a}_{n+1}}+4\left( n+1 \right) \right]=\left( n+2 \right)\left( {{a}_{n}}+4n \right) \\
& \frac{{{a}_{n+1}}+4\left( n+1 \right)}{{{a}_{n}}+4n}=\frac{n+2}{n} \\
& ...... \\
\end{align}\)
