若$f(x)=\begin{cases}\sin x, & x < 0\\-ax, & x\geq0\end{cases}$在$x = 0$处可导，求$a$的值.

$\lim\limits_{x \to 1}\dfrac{\ln x}{x - 1}$.

已知$\int f(x)dx = e^{2x}+C$，$\int g(x)dx=\sqrt{2x}+C$，则$\int [f(x)+g(x)]dx =$（　　）.