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 x be distance from +12 μC , then 0.6 - x from -3 μC . (12 × 10⁻⁶/x²) = (3 × 10⁻⁶/(0.6 - x)²) , 12 (0.6 - x)² = 3 x² . 4 (0.36 - 1.2 x + x²) = x² , 1.44 - 4.8 x + 4 x² = x² . 3 x² - 4.8 x + 1.44 = 0 , x