When \(a \ne 0\), there are two solutions to \(ax^2 + bx + c = 0\) and they are $$x = {-b \pm \sqrt{b^2-4ac} \over 2a}.$$ $${𝐅}_2=k\frac{q_1{q}_2{\widehat{𝐫}}_{21}}{r_{21}^2}$$