Two very long parallel wires 1.0m apart lie on the ground

[superflybob]

Homework Statement

Two very long parallel wires 1.0m apart lie on the ground carrying currents 4.0A and 6.0A in the same direction.
How far from the 4. wire are the magnetic field completely cancelled? 1.0m on the other side of the 4.0A wire, what is the magnitude of the magnetic field?

Homework Equations

B= UoI/2pir; B = (UoI/4pix)(cos alpha + cos betta) ; F/L = UoI1I2/2pid

The Attempt at a Solution

I have attempted to use the magnetic field equations in that they are both moving in same direction; the wires will attract each other meaning that they will be opposite signs, but still can't find the solution. I also tried using the Force per length but am not sure how to truly approach the problem.[/B]

 

[Simon Bridge]

The magnetic force is not in the same direction everywhere.
Start by drawing a picture and working out which direcetion a compass needle points on each side of the wires.