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$\frac{\text{d}x}{\text{d}y}$
$\lim_{n \rightarrow +\infty} \frac{n-1}{n(n+1)(n+2)}$
$\begin{cases}a & x = 0\b & x > 0\end{cases}$
$\begin{cases}a & x = 0\b & x > 0\end{cases}$
$\begin{cases}a & x = 0\b & x > 0\end{cases}\frac{-b\pm\sqrt{b^2-4ac}}{2a}$
$\frac{-b\pm\sqrt{b^2-4ac}}{2a}$