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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 (1,2,2)(1,2,2) on the line L:x−11=y+1−1=z−22\mathrm{L}: \frac{x-1}{1}=\frac{y+1}{-1}=\frac{z-2}{2}. Let the line r⃗=(−i^+j^−2k^)+λ(i^−j^+k^),λ∈R\vec{r}=(-\hat{i}+\hat{j}-2 \hat{k})+\lambda(\hat{i}-\hat{j}+\hat{k}), \lambda \in \mathbf{R}, intersect the line L at Q . Then 2(PQ)22(\mathrm{PQ})^2 is equal to :Let P be the foot of the perpendicular from the point (1,2,2) on the line L: (x-1)/(1)=(y+1)/(-1)=(z-2)/(2) . Let theLet P be the foot of the perpendicular from the point (1,2,2) on the line L: (x-1)/(1)=(y+1)/(-1)=(z-2)/(2) . Let theLet P be the foot of the perpendicular from the point (1,2,2) on the line L: (x-1)/(1)=(y+1)/(-1)=(z-2)/(2) . Let the

Options

  1. A25
  2. B19
  3. C29
  4. D27

Correct answer

D. 27

Step-by-step solution

General point on line L:x−11=y+1−1=z−22\mathrm{L}: \frac{x-1}{1}=\frac{y+1}{-1}=\frac{z-2}{2} is (λ+1,−λ−1,2λ+2)(\lambda+1,-\lambda-1,2 \lambda+2) Let P be the foot of the perpendicular from the point (1,2,2) on the line L: (x-1)/(1)=(y+1)/(-1)=(z-2)/(2) . Let the
DR's of PM are (λ,−λ−3,2λ)(\lambda,-\lambda-3,2 \lambda) PM⊥LP M \perp L ⇒λ+(−1)(−λ−3)+2(2λ)=0⇒6λ+3=0\begin{aligned} & \Rightarrow \lambda+(-1)(-\lambda-3)+2(2 \lambda)=0 \\ & \Rightarrow 6 \lambda+3=0 \end{aligned}Let P be the foot of the perpendicular from the point (1,2,2) on the line L: (x-1)/(1)=(y+1)/(-1)=(z-2)/(2) . Let the
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}<imgsrc="https://cdn−question−pool.getmarks.app/pyq/jeemain/tv00fIUHlp5piJsZzeDfj2UVox06HIZYHs0AXJfoI.original.fullsize.png"><br><img src="https://cdn-question-pool.Quantrex.app/pyq/jee_main/tv00fIUHl_p5piJ_sZzeDfj2UVox06HIZYHs0AXJfoI.original.fullsize.png"><br>\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}$$
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