Mathematics · 3D Geometry

JEE Main 2026 — 4 April, Evening Shift — Question 38

If (2α+1,α2−3α,α−12)\left(2\alpha +1,\alpha^{2} - 3\alpha, \frac{\alpha - 1}{2}\right) is the image of (α,2α,1)(\alpha ,2\alpha ,1) in the line x−23=y−12=z1\frac{x - 2}{3} = \frac{y - 1}{2} = \frac{z}{1}, then the possible value(s) of α\alpha is(are):

  1. Option A:

    Only 3

    Correct
  2. Option B:

    Only 3 and −1-1

  3. Option C:

    Only 3, 14\frac{1}{4} and −1-1

  4. Option D:

    Only 3 and 14\frac{1}{4}

Answer: A

Step-by-step solution

∴P\therefore \mathrm{P} is mid point of AB and lies on the given line ⇒P(3α+12,α2−α2,α+14)\Rightarrow \mathrm{P}\left(\frac{3 \alpha+1}{2}, \frac{\alpha^{2}-\alpha}{2}, \frac{\alpha+1}{4}\right) Now put coordinates of P in the line ⇒3α+12−23=α2−α2−12=α+14\Rightarrow \frac{\frac{3 \alpha+1}{2}-2}{3}=\frac{\frac{\alpha^{2}-\alpha}{2}-1}{2}=\frac{\alpha+1}{4} ⇒α−12=α+14=α2−α−24\Rightarrow \frac{\alpha-1}{2}=\frac{\alpha+1}{4}=\frac{\alpha^{2}-\alpha-2}{4} ⇒α=3\Rightarrow \alpha=3 Now for α=3\alpha=3, clearly AB is perpendicular to 3i^+2j^+k3 \hat{\mathrm{i}}+2 \hat{\mathrm{j}}+\mathrm{k} for α=3\alpha=3 point B is image of point A

Solution figure

Answer key and solution verified before publishing.

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Exam
JEE Main 2026
Subject
Mathematics
Chapter
3D Geometry
Topic
Straight Lines in 3D Geometry
If (2α +1,α 2 - 3α, α - 1/2 ) is the image of (α ,2α ,1) in the line… | JEE Main 2026 PYQ with Solution · DhiX AI