[PS] Rework parts of tests section, more changes to come

semester4/ps/ps-jh/parts/09_combinatorics/03_binomial-theorem.tex

@@ -0,0 +1,4 @@
+\subsection{Binomialsatz}
+\[
+    (x + y)^n = \sum_{i = 0}^{n} {n \choose i} x^i y^{n - i} = \sum_{i = 0}^{n} {n \choose i} x^{n - i} y^i
+\]