The potential energy of an electron in the hydrogen atom is $\pu{-6.8 eV}.$ Indicate the excited stage in which electron is present.
Total energy would be equal to $\pu{-3.4 eV}.$ I used the formula
$$-13.6\left(\frac{1}{1^2} - \frac{1}{n^2}\right) = \pu{-3.4 eV};$$
$$n^2 - 1/ n^2 = 4.$$
I got answer as $3n^2 = 4,$ which is obviously not correct. Where am I going wrong? I need help either with the formula or calculation I did wrong.