[填空题]
A military helicopter flies from an airbase a/*rll3x0dhh et A to a battlefield at t 95r qmhh)ip:d*u hd2B and then to a hospital at H . The routes taken by the helicopter are given t)phrd: u h*mq5 2hdi9by the vectors
$\overrightarrow{\mathrm{AB}}=\left(\begin{array}{c}
-140 \\
70
\end{array}\right) \text { and } \overrightarrow{\mathrm{BH}}=\left(\begin{array}{c}
165 \\
-20
\end{array}\right) \text {. }$
Distances are measured in kilometres.
1. Determine the vector $ \overrightarrow{\mathrm{AH}}$ .
After evacuating wounded soldiers from the battlefield to the front-line hospital, the helicopter returns back to the airbase.$\begin{pmatrix}
a \\
b
\end{pmatrix}$ a = b =
2. Write down the vector that describes this return flight.$\begin{pmatrix}
a \\
b
\end{pmatrix}$ a = b =
3. Find the direct distance from the hospital to the airbase. ≈ km
