Verified Solution • 2025–26 Session moderate

QJEEM22Mac87a: JEE Main 2022 Mathematics - Class 12 JEEM22Mac87a Solution: If the shortest distance between the lines and is , then the…

If the shortest distance between the lines x−12=y−23=z−3λ{{x - 1} \over 2} = {{y - 2} \over 3} = {{z - 3} \over \lambda } and x−21=y−44=z−55{{x - 2} \over 1} = {{y - 4} \over 4} = {{z - 5} \over 5} is 13{1 \over {\sqrt 3 }} , then the sum of all possible value of λ\lambda is :

Multiple Choice Options

  • A 6
  • B 12
  • C 15
  • D 16

Step-by-Step Verified Solution

Let a→1=i^+2j^+3k^{\overrightarrow a _1} = \widehat i + 2\widehat j + 3\widehat k

a→2=2i^+4j^+5k^{\overrightarrow a _2} = 2\widehat i + 4\widehat j + 5\widehat k

p→=2i^+3j^+λk^, q→=i^+4j^+5k^\overrightarrow p = 2\widehat i + 3\widehat j + \lambda \widehat k,\,\overrightarrow q = \widehat i + 4\widehat j + 5\widehat k

∴\therefore p→×q→=(15−4λ)i^−(10−λ)j^+5k^\overrightarrow p \times \overrightarrow q = (15 - 4\lambda )\widehat i - (10 - \lambda )\widehat j + 5\widehat k

a→2−a→1=i^+2j^+2k^{\overrightarrow a _2} - {\overrightarrow a _1} = \widehat i + 2\widehat j + 2\widehat k

∴\therefore Shortest distance

=∣(15−4λ)−2(10−λ)+10(15−4λ)2+(10−λ)2+25∣=13= \left| {{{(15 - 4\lambda ) - 2(10 - \lambda ) + 10} \over {\sqrt {{{(15 - 4\lambda )}^2} + {{(10 - \lambda )}^2} + 25} }}} \right| = {1 \over {\sqrt 3 }}

⇒3(5−2λ)2=(15−4λ)2+(10−λ)2+25\Rightarrow 3{(5 - 2\lambda )^2} = {(15 - 4\lambda )^2} + {(10 - \lambda )^2} + 25

⇒5λ2−80λ+275=0\Rightarrow 5{\lambda ^2} - 80\lambda + 275 = 0

∴\therefore Sum of values of λ=805=16\lambda = {{80} \over 5} = 16

Related Learning Resources & Exam Preparation