a) A charge of 1C is affixed to the x axis at 20cm and a charge
of 4C is affixed at -10cm, where must a charge of -10C be placed in
order to have zero electrostatic force on it?
b) If instead, a charge of -3C is placed somewhere on the
x-axis, where must it be placed so that the origin (0,0) will
experience zero electric field?
Please include detailed NEAT explanation.