[tex]9e^{2}f=49[/tex] Divide by the coefficient of e², multiply by f/f, then take the square root. [tex]e^{2}=\dfrac{49}{9f}=\dfrac{49}{9f}\cdot \dfrac{f}{f}=\dfrac{49f}{9f^{2}}\\\\e=\pm \dfrac{\sqrt{7^{2}f}}{\sqrt{(3f)^{2}}}\\\\e=\pm \dfrac{7\sqrt{f}}{3f}[/tex]
