( a +
b )²
= a² + 2ab + b² ,
( a – b )² = a² – 2ab + b² ,
a² – b² = ( a + b ) ( a – b ),
( a + b )³ = a³ + 3a² b + 3ab² + b³ ,
( a – b )³ = a ³ – 3a² b + 3ab² – b³ ,
a³ + b³ = ( a + b )( a² – ab + b² ) ,
a³ – b³ = ( a – b )( a ² + ab + b² ) .
