( a ×a×a ) × ( a×a×a) ×a , legea este asociativa
↓ ↓
( 3a + 12 ) × ( 3a + 12 ) × a
a×a = a +a+ 6 = 2a +6
( a ×a ) × a = a×a + a + 6 = 2a + 6 + a + 6 = 3a + 12
( 3a + 12 ) × ( 3a + 12 ) = ( 3a + 12 ) + ( 3a + 12 ) + 6 = 6a + 30
final : ( 6a + 30 ) × a = ( 6a + 30 ) + a + 6 = 7a + 36