Addition of velocities. relativity.

[night]

Homework Statement

Show that the addition of velocities implies that:
a)if V < c in any inertial frame, then V < c in any other.
b)If V=c in one inertial frame, then V=c in the other.
c)If V>c in any inertial frame, then V>c in any other inertial frame.

Homework Equations

Vx'=(Vx-c)/(1-vVx/c^2)

The Attempt at a Solution

I did b) and I can't do a) and c)

 

[vela]

Show us what you tried for part a.