Electric Field Example Problem

1. Two charges, one of -1.0 µC and the other of -3.0 µC are 40 cm apart.
• (a)Where should a charge of -0.1 µC be placed on the line between the other charges in order that there be no resultant force on it ?
• (b)Where should a charge of +0.1µC be placed in order that there be no resultant force on it ?