1.An electric charge q1 (-e) is located at the origin. A second electric charge q2 (-4e) is located at a distance d from the origin on the x-axis. A third charge q3 (+e) is located a distance x, which is less than d, on the x-axis between q1 and q2. In terms of d, what is the distance x where the net electric force is zero? 2. I just need a pretty thorough explanation. Not a broken stream of steps. F = F1 - F2 F = 0 then F1 = F2 kq1q3 / x^2 = kq2q3 / (d-x)^2 q1 / x^2 = q2 / (d-x)^2 (d-x)^2 - (q2/q1)x^2 = 0 ..... I've made it as far as this and then asked for help on another site. Someone responded with the following: F = F1 - F2 [forces are opposite] F = 0 then F1 = F2 kq1q3 / x^2 = kq2q3 / (d-x)^2 q1 / x^2 = q2 / (d-x)^2 (d-x)^2 - (q2/q1)x^2 = 0 (1-q2/q1)x^2 -2dx + d^2 = 0 -3x^2 -2dx + d^2 = 0 x = [2d +- (4d^2 - 12d^2)^1/2] / (-6) x = d/3 I have no clue what he/she did after line 9 (-3x^2 -2dx+d^2 = 0).