
L=3x+1=5y+3=7z+5PQ=1x−715=4y−732=7z−7=λ ⇒Q(λ+715,4λ+732,7λ+7) Since Q lies on line L $\begin{aligned}
& \text { So, } \frac{\lambda+\frac{15}{7}+1}{3}=\frac{7 \lambda+7+5}{7} \
& \Rightarrow 7 \lambda+22=21 \lambda+36 \
& \Rightarrow \lambda=-1 \
& \therefore \text { Point } Q\left(\frac{8}{7}, \frac{4}{7}, 0\right) \
& \mathrm{PQ}=\sqrt{\left(\frac{15}{7}-\frac{8}{7}\right)^2+\left(\frac{32}{7}-\frac{4}{7}\right)^2+(7-0)} \
& \mathrm{PQ}=\sqrt{66} \
& \Rightarrow(\mathrm{PQ})^2=66
\end{aligned}$