\[1)\ z_{1} + z_{2} = z_{2} + z_{1}\]
\[\left( a_{1} + b_{1}i \right) + \left( a_{2} + b_{2}i \right) =\]
\[= \left( a_{2} + b_{2}i \right) + \left( a_{1} + b_{1}i \right)\]
\[\left( a_{1} + a_{2} \right) + \left( b_{1} + b_{2} \right)i =\]
\[= \left( a_{1} + a_{2} \right) + \left( b_{1} + b_{2} \right)i.\]
\[Что\ и\ требовалось\ доказать.\]
\[2)\ z_{1}z_{2} = z_{2}z_{1};\]
\[\left( a_{1} + b_{1}i \right)\left( a_{2} + b_{2}i \right) =\]
\[= \left( a_{2} + b_{2}i \right)\left( a_{1} + b_{1}i \right)\]
\[a_{1}a_{2} + a_{1}b_{2}i + a_{2}b_{1}i - b_{1}b_{2} =\]
\[= a_{1}a_{2} + a_{2}b_{1}i + a_{1}b_{2}i - b_{1}b_{2}\]
\[\left( a_{1}a_{2} - b_{1}b_{2} \right) + \left( a_{1}b_{2} + a_{2}b_{1} \right)i =\]
\[= \left( a_{1}a_{2} - b_{1}b_{2} \right) + \left( a_{1}b_{2} + a_{2}b_{1} \right)i.\]
\[Что\ и\ требовалось\ доказать.\]
\[3)\ \left( z_{1}z_{2} \right)z_{3} = z_{1}\left( z_{2}z_{3} \right);\]
\[\left( z_{1}z_{2} \right)z_{3} =\]
\[= \left( \left( a_{1} + b_{1}i \right)\left( a_{2} + b_{2}i \right) \right)\left( a_{3} + b_{3}i \right) =\]
\[z_{1}\left( z_{2}z_{3} \right) =\]
\[= \left( a_{1} + b_{1}i \right)\left( \left( a_{2} + b_{2}i \right)\left( a_{3} + b_{3}i \right) \right) =\]
\[Что\ и\ требовалось\ доказать.\]
\[4)\ \left( z_{1} + z_{2} \right) + z_{3} = z_{1} + \left( z_{2} + z_{3} \right)\]
\[\left( z_{1} + z_{2} \right) + z_{3} =\]
\[z_{1} + \left( z_{2} + z_{3} \right) =\]
\[Что\ и\ требовалось\ доказать.\]
\[5)\ z + 0 = z\]
\[(a + bi) + 0 = a + bi\]
\[a + bi = a + bi.\]
\[Что\ и\ требовалось\ доказать.\]
\[6)\ z \bullet 1 = z\]
\[(a + bi) \bullet 1 = a + bi\]
\[a + bi = a + bi.\]
\[Что\ и\ требовалось\ доказать.\]