1. Do $d\perp \Delta:3x-6y+5=0$
$\Rightarrow d$ có dạng: $6x+3y+m=0$
d qua $M(-2,5)$
$\Rightarrow 6.(-2)+3.5+m=0$
$\Leftrightarrow m=-3$
$\Rightarrow$ pttq:$6x+3y-3=0$
$\Leftrightarrow 2x+y-1=0$
2. Tâm $I(\frac{-3}{-2},\frac{12}{-2})$
$\Rightarrow I(\frac{3}{2},-6)$
Bán kính
$R=\sqrt{a^2+b^2-c}=\sqrt{(\frac{3}{2})^2+(-6)^2-(-1)}$
$\Rightarrow R=\dfrac{\sqrt{157}}{2}$
