\[\begin{aligned}
&\begin{cases}
f(y_n)-f(x_0)=f'(x_0)(y_n-x_0)+\alpha_n(y_n-x_0) \\
f(x_n)-f(x_0)=f'(x_0)(x_n-x_0)+\beta_n(x_n-x_0) \\
\end{cases} \\
\Rightarrow &
\frac{f(y_n)-f(x_n)}{y_n-x_n}=f'(x_0)+\frac{\alpha_n(y_n-x_0)}{y_n-x_n}+\frac{\beta_n(x_n-x_0)}{y_n-x_N} \\
\Rightarrow &
f'(x_0)=\lim_{n \to \infty} \frac{f(y_n)-f(x_n)}{y_n-x_n}
\end{aligned}
\]
标签：begin,12,end,alpha,微积分,beta,随缘,frac,cases
来源： https://www.cnblogs.com/nekko/p/15463270.html