Question:
If the line $\frac{x-2}{3}=\frac{y+1}{2}=\frac{z-1}{-1}$ intersects the palne $2 x+3 y-z+13=0$ at a point $P$ and the plane $3 x+y+4 z=16$ at a point $Q$, then PQ is equal to :
Correct Option: 1
Solution:
$\frac{x-2}{3}=\frac{y+1}{2}=\frac{z-1}{-1}=\lambda$
$\mathrm{x}=3 \lambda+2, \mathrm{y}=2 \lambda-1, \mathrm{z}=-\lambda+1$
Intersection with plane $2 x+3 y-z+13=0$
$2(3 \lambda+2)+3(2 \lambda-1)-(-\lambda+1)+13=0$
$13 \lambda+13=0 \quad \lambda=-1$
$\therefore \quad P(-1,-3,2)$
Intersection with plane
$3 x+y+4 z=16$
$3(3 \lambda+2)+(2 \lambda-1)+4(-\lambda+1)=16$
$\lambda=1$
$\mathrm{Q}(5,1,0)$
$\mathrm{PQ}=\sqrt{6^{2}+4^{2}+2^{2}}=\sqrt{56}=2 \sqrt{14}$