3x+6=2y=1z+1=λ....(1)x=3λ−6,y=2λ,z=λ−14x−7=3y−9=2z−4=μ....(2) x=4μ+7,y=3μ+9,z=2μ+4 3λ−6=4μ+7⇒3λ−4μ=13 …(3)×2 2λ=3μ+9⇒2λ−3μ=9 …(4)×3 $\begin{array}{c}
6 \lambda-8 \mu=26 \
6 \lambda-9 \mu=27 \
-\quad+\quad- \
\hline\mu=-1
\end{array}\begin{gathered}
\Rightarrow 3 \lambda-4(-1)=13 \
3 \lambda=9 \
\lambda=3
\end{gathered}int.point(3,6,2) ;(7,8,9)\mathrm{d}^2=16+4+49=69Ans.\mathrm{d}^2+6=69+6=75$