Question

Q/ Find the parametric equations of the line joining the points P1( 1, 1, -1) and P2( 1, 2, 0)?

Answer 1

using the usual rules, you get
(x-1)/(1-1) = (y-1)/(2-1) = (z+1)/(0+1)

so, what do you need to do to make it work here?