JEE Main 202529 JanuaryEvening Shift
- Exam
- JEE Main
- Year
- 2025
- Date
- 29 January
- Shift
- Evening Shift
- Subject
- Mathematics
- Chapter
- Three Dimensional Geometry
JEE Main 2025 · 29 January · Evening Shift · Mathematics · Three Dimensional Geometry
Let P be the foot of the perpendicular from the point (1,2,2) on...
Let P be the foot of the perpendicular from the point on the line . Let the line , intersect the line L at Q . Then is equal to :


Options
- A25
- B19
- C29
- D27
Correct answer
D. 27
Step-by-step solution
General point on line
is

DR's of PM are
P\left(\frac{1}{2}, \frac{-1}{2}, 1\right)$ Let another line $L^{\prime}: \frac{x+1}{1}=\frac{y-1}{-1}=\frac{z+2}{1}$ General point on line $L^{\prime}$ is $(\mu-1,-\mu+1, \mu-2)$ Point of intersection of line $L$ and $L^{\prime}$ is\begin{array}{l|l} \lambda+1=\mu-1 & 2 \lambda+2=\mu-2 \\ \Rightarrow \mu-\lambda=2 \ldots(1) & \Rightarrow 2 \lambda=\mu-4 \end{array}\begin{aligned} & Q(-1,1,-2) \\ & 2(P Q)^2=2\left(\left(\frac{1}{2}+1\right)^2+\left(\frac{-1}{2}-1\right)^2+(1+2)^2\right) \\ & =2\left(\frac{9}{4}+\frac{9}{4}+9\right) \\ & =27\end{aligned}$$
DR's of PM are
P\left(\frac{1}{2}, \frac{-1}{2}, 1\right)$ Let another line $L^{\prime}: \frac{x+1}{1}=\frac{y-1}{-1}=\frac{z+2}{1}$ General point on line $L^{\prime}$ is $(\mu-1,-\mu+1, \mu-2)$ Point of intersection of line $L$ and $L^{\prime}$ is\begin{array}{l|l} \lambda+1=\mu-1 & 2 \lambda+2=\mu-2 \\ \Rightarrow \mu-\lambda=2 \ldots(1) & \Rightarrow 2 \lambda=\mu-4 \end{array}\begin{aligned} & Q(-1,1,-2) \\ & 2(P Q)^2=2\left(\left(\frac{1}{2}+1\right)^2+\left(\frac{-1}{2}-1\right)^2+(1+2)^2\right) \\ & =2\left(\frac{9}{4}+\frac{9}{4}+9\right) \\ & =27\end{aligned}$$