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JEE Main 20264 AprilMorning Shift
Exam
JEE Main
Year
2026
Date
4 April
Shift
Morning Shift
Subject
Mathematics
Chapter
Three Dimensional Geometry

JEE Main 2026 · 4 April · Morning Shift · Mathematics · Three Dimensional Geometry

A line with direction ratios 1, -1, 2 intersects the lines (x)/(2)...

A line with direction ratios 1,−1,21, -1, 2 intersects the lines x2=y3=z+13\dfrac{x}{2} = \dfrac{y}{3} = \dfrac{z+1}{3} and x+1−1=y−21=z4\dfrac{x+1}{-1} = \dfrac{y-2}{1} = \dfrac{z}{4} at the points PP and QQ, respectively. If the length of the line segment PQPQ is α\alpha, then 225α2225\alpha^2 is equal to:

Options

  1. A10241024
  2. B10141014
  3. C11041104
  4. D12041204

Correct answer

B. 10141014

Step-by-step solution

Let the coordinates of PP on the first line be (2λ,3λ,3λ−1)(2\lambda, 3\lambda, 3\lambda - 1).

Let the coordinates of QQ on the second line be (−μ−1,μ+2,4μ)(-\mu - 1, \mu + 2, 4\mu).

The direction ratios of the line segment PQPQ are proportional to 1,−1,21, -1, 2. Thus, we can write:

−μ−1−2λ1=μ+2−3λ−1=4μ−3λ+12=k\dfrac{-\mu - 1 - 2\lambda}{1} = \dfrac{\mu + 2 - 3\lambda}{-1} = \dfrac{4\mu - 3\lambda + 1}{2} = k

This gives the system of equations:

−μ−2λ−1=k-\mu - 2\lambda - 1 = k

μ−3λ+2=−k\mu - 3\lambda + 2 = -k

4μ−3λ+1=2k4\mu - 3\lambda + 1 = 2k

Adding the first two equations gives:

−5λ+1=0⇒λ=15-5\lambda + 1 = 0 \Rightarrow \lambda = \dfrac{1}{5}

Substituting λ=15\lambda = \dfrac{1}{5} into the first and third equations:

−μ−75=k⇒μ+k=−75-\mu - \dfrac{7}{5} = k \Rightarrow \mu + k = -\dfrac{7}{5}

4μ+25=2k⇒2μ−k=−154\mu + \dfrac{2}{5} = 2k \Rightarrow 2\mu - k = -\dfrac{1}{5}

Adding these two equations gives:

3μ=−85⇒μ=−8153\mu = -\dfrac{8}{5} \Rightarrow \mu = -\dfrac{8}{15}

Substituting μ=−815\mu = -\dfrac{8}{15} into μ+k=−75\mu + k = -\dfrac{7}{5}:

−815+k=−2115⇒k=−1315-\dfrac{8}{15} + k = -\dfrac{21}{15} \Rightarrow k = -\dfrac{13}{15}

The vector PQ→\overrightarrow{PQ} is (k,−k,2k)(k, -k, 2k). The length of the line segment PQPQ is α=k2+(−k)2+(2k)2=6k2\alpha = \sqrt{k^2 + (-k)^2 + (2k)^2} = \sqrt{6k^2}.

Thus, α2=6k2=6(−1315)2=6×169225=1014225\alpha^2 = 6k^2 = 6 \left(-\dfrac{13}{15}\right)^2 = 6 \times \dfrac{169}{225} = \dfrac{1014}{225}.

Therefore, 225α2=1014225\alpha^2 = 1014.

Answer: 10141014
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