Update 11_nearly_free_electron_model_solutions.md - polish

src/11_nearly_free_electron_model_solutions.md

@@ -165,11 +165,11 @@ and
 
 In the limit $\kappa a \gg 1$ (i.e., where the distance between the delta functions is large compared to the width of $|n\rangle$), the onsite energy becomes
 $$
-\langle n|H|n \rangle = \epsilon_0 - 2\kappa \lambda e^{-2\kappa a}
+\langle n|H|n \rangle = \epsilon_0(1-4 e^{-2\kappa a})
 $$
 and the hopping becomes
 $$
-\langle n-1|H|n \rangle = (\epsilon_0 \kappa a  - \kappa \lambda) e^{-\kappa a}
+\langle n-1|H|n \rangle = \epsilon_0 (\kappa a  - 2) e^{-\kappa a}
 $$
 
 ### Subquestion 4