Q.

If the shortest distance between the lines x–λ–2=y–21=z–11 and x–31=y–1–2=z–21 is 1, then the sum of all possible values of λ is:          [2024]

1 23  
2 0  
3 33  
4 –23  

Ans.

(1)

The shortest distance between the given lines is given by

d=||x2–x1y2–y1z2–z1a1b1c1a2b2c2|(a1b2–a2b1)2+(b1c2–b2c1)2+(c1a2–c2a1)2|

⇒ 1=||3–λ–11–2111–21|(3)2+(3)2+(3)2|

⇒ 1=|(3–λ)(3)+1(–3)+1(3)|27

⇒ 33=33–3λ  or  –33=33–3λ

⇒ λ=0 or 63=3λ ⇒ λ=23

∴  The sum of possible values of λ=0+23=23.