[1] ( a + b )² = a² + 2ab + b² , [2] ( a – b )² = a² – 2ab + b² ,
[3] ( a + b ) ( a – b ) = a² – b²,
[4] ( a + b )³ = a³ + 3a²b + 3ab² + b³ ,
[5] ( a – b )³ = a ³ – 3a²b + 3ab² – b³ [6] ( a + b )( a² – ab + b²) = a³ + b³ , [7] ( a – b )( a ² + ab + b² ) = a³ – b³ .