Update 1_complex_numbers.md (cont. of last commit) Forgot to change the second line

src/1_complex_numbers.md

@@ -72,7 +72,7 @@ Check this!
 !!! check "Example:"
     $$\begin{align} 
     \frac{1 + 2{\rm i}}{1 - 2{\rm i}} &= \frac{(1 + 2{\rm i})(1 + 2{\rm i})}{1^2 + 2^2} = \frac{1+4{\rm i} -4}{5}\\
-    & = -\frac{3}{5} + {\rm i} \frac{8}{5}
+    & = -\frac{3}{5} + {\rm i} \frac{4}{5}
     \end{align}$$
 
 ### Visualization: the complex plane