
Equation of normal to parabola
y2=8x is y=mx−4m−2m3
passes through (0,−6) we get
$\begin{aligned}
& -6=-4 \mathrm{m}-2 \mathrm{m}^3 \
& \Rightarrow \mathrm{m}^3+2 \mathrm{m}-3=0 \
& \Rightarrow(\mathrm{m}-1)\left(\mathrm{m}^2+\mathrm{m}+3\right)=0 \Rightarrow \mathrm{m}=-1 \
& \mathrm{P}=\left(\mathrm{am}^2,-2 \mathrm{am}\right)=(2,-4) \
& \therefore \text { Shortest distance }=\mathrm{PC}-\mathrm{r} \
& =(2 \sqrt{2}-1)
\end{aligned}$