When $a \ne 0$, there are two solutions to $(ax^2 + bx + c = 0)$ and they are $$ x = {-b \pm \sqrt{b^2-4ac} \over 2a} $$
Maxwell’s equations:
| equation | description |
|---|---|
| $\nabla \cdot \vec{\mathbf{B}} = 0$ | divergence of $\vec{\mathbf{B}}$ is zero |
| $\nabla \times \vec{\mathbf{E}}\, +\, \frac1c\, \frac{\partial\vec{\mathbf{B}}}{\partial t} = \vec{\mathbf{0}}$ | curl of $\vec{\mathbf{E}}$ is proportional to the rate of change of $\vec{\mathbf{B}}$ |
| $\nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} = \frac{4\pi}{c}\vec{\mathbf{j}} \nabla \cdot \vec{\mathbf{E}} = 4 \pi \rho$ | wha? |