[tex]\sqrt{x^2 -\dfrac nm} = \dfrac{a^2}b\\\\\implies x^2 - \dfrac nm = \dfrac{a^4}{b^2}\\\\\implies x^2 = \dfrac{a^4}{b^2} + \dfrac nm}\\\\\implies x = \pm \sqrt{ \dfrac{a^4}{b^2} + \dfrac nm}}[/tex]
