The equation of straight line passing through the point(a, b, c) and parallel to z- axis, is
[MP PET 1995; Pb. CET 2000]
The line through (a,b,c) is x−al=y−bm=z−cn ....(i)
Since the line is parallel to z-axis, therefore any point on this line will be of the form (a,b,z1).
Also any point on line (i) is (lr+a,mr+b,nr+c).
Hence lr+a+=amr+b=b ⇒l=m=0
Hence the line will be x−a0=y−b0=z−c1.