Let S be the set of all values of λ, for which the shortest distance between the lines x-λ 0= y-3 4= z+6 1and x+λ 3= y -4= z-6 0 is 13. Then…
JEE Main 2023 — Mathematics Vectors & 3D Geometry
2023mcqmedium
Let S be the set of all values of λ, for which the shortest distance between the lines 0x−λ=4y−3=1z+6and 3x+λ=−4y=0z−6 is 13. Then 8∣λ∈S∑λ∣ is equal to
Official previous-year question
Held on 15 Apr 2023 · Verified 6 Jul 2026.
Options
A
306
B
304
C
308
D
302
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Solution
The given lines are0x−λ=4y−3=1z+6and 3x+λ=−4y=0z−6
We know that the shortest distance between two lines is d=|\frac{({\vec{a}}_{2}-{\vec{a}}_{1})\cdot ({\vec{n}}_{1}\times {\vec{n}}_{2})}{|{\vec{n}}_{1}\times {\vec{n}}_{2}|}|&d=13(\text{given})
⇒n1×n2=∣i^03j^4−4k^10∣=4i^+3j^−12k^
Now using the above formula of distance we get,
⇒∣16+9+144(2λi^+3j^−12k^)⋅(4i^+3j^−12k^)∣=13
⇒∣13(2λi^+3j^−12k^)⋅(4i^+3j^−12k^)∣=13
⇒∣8λ+9+144∣=169
⇒∣8λ+153∣=169
⇒8λ=±169−153
⇒λ=816,8−322
⇒8∣λ∈s∑λ∣=8∣816−8322∣=306
Hence this is the correct option.
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