Solve for f
f=-\frac{2\left(2x+1\right)}{x^{2}}
x\neq 0
Solve for x (complex solution)
\left\{\begin{matrix}x=\frac{\sqrt{2\left(2-f\right)}-2}{f}\text{; }x=-\frac{\sqrt{2}\left(\sqrt{2-f}+\sqrt{2}\right)}{f}\text{, }&f\neq 0\\x=-\frac{1}{2}\text{, }&f=0\end{matrix}\right.
Solve for x
\left\{\begin{matrix}x=\frac{\sqrt{2\left(2-f\right)}-2}{f}\text{; }x=-\frac{\sqrt{2}\left(\sqrt{2-f}+\sqrt{2}\right)}{f}\text{, }&f\neq 0\text{ and }f\leq 2\\x=-\frac{1}{2}\text{, }&f=0\end{matrix}\right.
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fx^{2}+2=-4x
Subtract 4x from both sides. Anything subtracted from zero gives its negation.
fx^{2}=-4x-2
Subtract 2 from both sides.
x^{2}f=-4x-2
The equation is in standard form.
\frac{x^{2}f}{x^{2}}=\frac{-4x-2}{x^{2}}
Divide both sides by x^{2}.
f=\frac{-4x-2}{x^{2}}
Dividing by x^{2} undoes the multiplication by x^{2}.
f=-\frac{2\left(2x+1\right)}{x^{2}}
Divide -4x-2 by x^{2}.
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