At what position is the net electric field equal to zero?

[laxwarrior]

Two charges are separated by 1.0 m. Q1 has a negative charge of 4.2 µC and Q2 has a positive charge of 1.4 µC. At what position is the net electric field that is produced by both Q1 and Q2 equal to zero?

Extra Credit: If a +5.0 µC charge is placed at this position, what force would act on it as a result of Q1 and Q2?

 

[Stonebridge]

You need to show your attempt at this question before we can help.