((1-3i) ^2 - (1+3i) ^2) / ((1+3i) (1-3i)) = (1-6i+9i^2-1-9i^2-6i) / (1-9i^2) =
=-12i / (1+9) = - 1,2i
((1-3i) ^2 - (1+3i) ^2) / ((1+3i) (1-3i)) = (1-6i+9i^2-1-9i^2-6i) / (1-9i^2) =
=-12i / (1+9) = - 1,2i