[填空题]
The coordinates of point P are(−4,6) and the coordinates a3 ms3jk a o9h6v9ceq4of7 z+j(mxl-ue axq- oe, point Q are(5,1). M is thjlx oa,eqx7-(+m z -eue midpoint of [PQ].
1.Find the coordinates of M.
$L_1$ is the line which passes through P and Q. (a,b) a= b=
2.Find the gradient of $L_1$.
A new line, $L_2$, is perpendicular to $L_1$ and passes through M. $m_{L_1}$ =
3.(1)Write down the gradient of $L_2$. $m_{L_2}$ =
(2)Write down the equation of $L_2$ in the form y=mx+c. m = c =
