Solve F=9*10^{9}Nm^2CC^2(1.9*10^-6C)-4.0*10^-6

$$F = 9 \times 10 ^ { 9 } Nm ^ { 2 } CC ^ { 2 } ( 1.9 \times 10 ^ { - 6 } C ) - 4.0 \times 10 ^ { - 6 }$$

Solve for C (complex solution)

$$\left\{\begin{matrix}C=\frac{i\times 684^{0.75}m^{-0.5}N^{-0.25}\sqrt[4]{250000F+1}}{34200}\text{; }C=\frac{684^{0.75}m^{-0.5}N^{-0.25}\sqrt[4]{250000F+1}}{34200}\text{; }C=-\frac{684^{0.75}m^{-0.5}N^{-0.25}\sqrt[4]{250000F+1}}{34200}\text{; }C=-\frac{i\times 684^{0.75}m^{-0.5}N^{-0.25}\sqrt[4]{250000F+1}}{34200}\text{, }&m\neq 0\text{ and }N\neq 0\\C\in \mathrm{C}\text{, }&\left(N=0\text{ or }m=0\right)\text{ and }F=-\frac{1}{250000}\end{matrix}\right.$$

Solve for C

$$\left\{\begin{matrix}\\C=0\text{, }&\text{unconditionally}\\C=\frac{\sqrt[4]{\frac{246924\left(250000F+1\right)}{N}}}{5700\sqrt{|m|}}\text{; }C=-\frac{\sqrt[4]{\frac{246924\left(250000F+1\right)}{N}}}{5700\sqrt{|m|}}\text{, }&\left(F\leq -\frac{1}{250000}\text{ and }N<0\text{ and }m\neq 0\right)\text{ or }\left(F\geq -\frac{1}{250000}\text{ and }N>0\text{ and }m\neq 0\right)\\C\in \mathrm{R}\text{, }&\left(N=0\text{ or }m=0\right)\text{ and }F=-\frac{1}{250000}\end{matrix}\right.$$

Solve for F

$$F=17100Nm^{2}C^{4}-0.000004$$