1. The problem statement, all variables and given/known data https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-xfp1/v/t1.0-9/12417589_10205411987170709_6390638921146727371_n.jpg?oh=e166de7d1246b4afacebe60bac5ce654&oe=570B03E4&__gda__=1460454017_6cad38b2934b81eeeccbeedf05704e4b 2. Relevant equations Electric potential 3. The attempt at a solution Is electric potential a vector quantity? So that mean both charges product electric potential and result in zero at P? How should i start for question 17a?