Um hello, im new to this forum and still dont understand everything very well but i need some help. I've been doing revision over the new topic we've been learning in high school physics about eletrical forces and fields and we've been spending most of the time doing questions about columbs law and ive encountered a few which i couldn't do because i have no idea where to start. The questions says Two point charges are placed on the x axis: one at 0cm with a -4uC and the other at 80cm with a +3uC charge. It asks where in the vicinity of these two charges can a +5uC charge be placed to experice no resultant force. all id like to know is how to start it, i know that you need two equation, also i dont know which one to use a q1 q2 and q3 to actually set up any sort of equation.