[填空题]
The line L has equ2pq cy4d2ryhb+ 7ul r(ym m)e0jywv jhjoqw);4 89z7nation $\mathbf{r}=\left(\begin{array}{c}4 \\ -1 \\ 0\end{array}\right)+t\left(\begin{array}{c}1 \\ 1 \\ -1\end{array}\right), t \in \mathbb{R}$ .
The point A has coordinates (4,8,-3) . The point B lies on L such that $\overrightarrow{\mathrm{AB}}$ is perpendicular to L .
1. Find $\overrightarrow{\mathrm{OB}}$ .$\left(\begin{array}{l}
a \\
b \\
c
\end{array}\right)$ a = b = c =
2. Find the shortest distance from A to L .
3. Find the coordinates of the reflection of the point A in the line L . (a,b,c) a = b = c =
