Answer:
20 cm
Explanation:
Te electric potential enery U = kq₁q₂/r were q₁ = 5 nC = 5 × 10⁻⁹ C and q₂ = -2 nC = -2 × 10⁻⁹ C and r = √(x - 2)² + (0 - 0)² +(0 - 0)² = x - 2. U = -0.5 µJ = -0.5 × 10⁻⁶ J, k = 9 × 10⁹ Nm²/C².
So r = kq₁q₂/U
x - 2 = kq₁q₂/U
x = 0.02 + kq₁q₂/U m
x = 0.02 + 9 × 10⁹ Nm²/C² × 5 × 10⁻⁹ C × -2 × 10⁻⁹ C/-0.5 × 10⁻⁶ J
x = 0.02 - 90 × 10⁻⁹ Nm²/-0.5 × 10⁻⁶ J
x = 0.02 + 0.18 = 0.2 m = 20 cm