${\left( {a + b} \right)^n} = \left( {\begin{array}{*{20}{c}}n\\0\end{array}} \right) \cdot {a^n} + \left( {\begin{array}{*{20}{c}}n\\1\end{array}} \right) \cdot {a^{n - 1}} \cdot b + \left( {\begin{array}{*{20}{c}}n\\2\end{array}} \right) \cdot {a^{n - 2}} \cdot {b^2} + ... + \left( {\begin{array}{*{20}{c}}n\\k\end{array}} \right) \cdot {a^{n - k}} \cdot {b^k} + ... + \left( {\begin{array}{*{20}{c}}n\\{n - 1}\end{array}} \right) \cdot a \cdot {b^{n - 1}} + \left( {\begin{array}{*{20}{c}}n\\n\end{array}} \right) \cdot {b^n}$ ahol $n \in N$; $a, b \in R$