Dear Akshat
r x a = b x a
(r – b) x a = 0
r – b is parallel to a
hence
r – b =
a
i.e.
r = b +
a
similarly, r x b = a x b can be written as
r = a +
b
for point of intersection of these lines
we get
b +
a = a +
b
=
= 1
hence the required point of intersection is
r = a+ b = i +j + 2 i – k = 3 i +j – k
hence option 3 is correct
regards
Arun (askIITians forum expert)
