Q.

If the lines x-12=y-23=z-3α and x-45=y-12=zβ intersect, then the absolute value of (β-α) is _______

1 3  
2 - 3  
3 13  
4 - 13  

Ans.

(1)

Given the lines x-12=2-y-3=z-3α and x-45=y-12=zβ intersect

So, point on first line (1,2,3) and point on second line (4,1,0)

Vector joining both points is -3i^+j^+3k^

Now vector along first line is 2i^+3j^+αk^

Also vector along second line is 5i^+2j^+βk^

Now these three vectors must be coplanar ⇒|23α52β-313|=0

⇒2(6-β)-3(15+3β)+α(11)=0

⇒α-β=3