Consider three infinitely long current carrying wires 1, 2, and 3 kept parallel to each other as shown

Given $i_1=i_2=i_3$

If  $F_1$= Net magnetic force per length acting on wire $i_1$ due to $i_2$ and $i_3$
$F_2$= Net magnetic force per length acting on wire $i_2$ due to $i_1$ and $i_3$
$F_3$= Net magnetic force per length acting on wire $i_3$ due to $i_1$ and $i_2$   
Then