Three charged particles are fixed to an x axis: Particle 1 of charge q1 = 2.1e-8 C is at position x=20 cm and particle 2 of charge q2 = 2.00q1 is at position x = 30 cm, particle 3 of charge q3 = -4.00q1 is at position x = 70 cm.
At what coordinate on the axis (other than infinity) is the net electric field produced by the three particles equal to zero?