5.4 Exercise 20

Point charges $q_{1} = q_{2} = 4.0 \times 10^{−6} \text{C}$ are fixed on the x-axis at $x = −3.0 \text{m}$ and $x = 3.0 \text{m} .$ What charge q must be placed at the origin so that the electric field vanishes at $x = 0 , y = 3.0 \text{m} ?$