Angular momentum of a particle problem

[yuki_meiseki]

Homework Statement

Two identical particles have equal but opposite momenta, p and -p, but they are not traveling along the same line show that the total angular momentum of this system does not depend on the choice of origin.

Homework Equations

L=r x p
Sum of torque = dL/dt

The Attempt at a Solution

Do not understand the problem at all.

 

[Dick]

Total angular momentum is r1xp+r2x(-p). If you change the origin, r1 changes to r1+d and r2 changes to r2+d. Conclusion?