Electrostatic Equilibrium

In the diagram shown $P$ is a point negative charge. Its weight is balanced by the electric force due to the fixed very long wire. The equilibrium of the particle is,

Three charges $+4 q,-q$ and $+4q$ are kept on a straight line at position $\left(0,0,0\right), \left(a,0,0\right)$ and $\left(2a,0,0\right)$, respectively. Considering that they are free to move along the $x$-axis only

Two positively charged spheres of masses $m_1$ and $m_2$, are suspended from a common point at the ceiling by identical insulating massless strings of length $l$. Charges on the two spheres are $q_1$ and $q_2$, respectively. At equilibrium both strings make the same angle $\theta$ with the vertical. Then