l1:x−12=y−23=z−34l2:x+21=y−32=z+14
Let 2r+1,3r+2,4r+3 be the point of intersection of l1 and l2
∴3r+2−32=2r+1+21=4r+3+14−−−(i)
r=−2
but r does not satisfy equatton (i)
∴ l1 and l2 are skew lines.
points (1,2,3) and (−2,3,−1) lies on l1 and l2
if three points are collinear (x1y1z1),(x2y2z2)(x3y3z3), then
△=∣∣
∣∣x1−x2y1−y2z1−z2x2−x3y2−y3z2−z3x3−x1y3−y1z3−z1∣∣
∣∣=0
checking colinearity of (1,1,1),(1,2,3),(−2,3,−1)
△=0 ∴ they are collinear.
Hence equation of line is (x−1)−3=(y−1)1=(z−1)−4