Practice question

**Coulomb's law** gives force between point charges as F = k·|q₁q₂|/r², k = 1/(4π ε₀) = 9×10⁹ N·m²/C², directed along line joining charges. Like charges repel, opposite attract, magnitude scales with product of charges and inverse square of separation r². Let distance from +6 μC be x , then from -4 μC is 0.25 - x . (k × 6 × 10⁻⁶/x²) = (k × 4 × 10⁻⁶/(0.25 - x)²) . (6/x²) = (4/(0.25 - x)²) , 6 (0.25 - x)² = 4 x² . 6 (0.0625 - 0.5 x + x²) = 4 x² , 0.375 - 3 x + 6 x² = 4