1. The problem statement, all variables and given/known data The equation x^2+3x-0.45=0 has two solutions x1=0.14 and x2=-3.14, these are supposed to be the locations at which the electric charge is in equilibrium with two other charges, should I use the first derivative to see at which location the charge will be stable? 2. Relevant equations x^2+3x-0.45=0 3. The attempt at a solution f’=2x+3, f’(x1)>0 so the charge is stable, is my reasoning correct?