legea : x× y =3 · ( x -2 ) ·( y -2 ) + 2
element neutru x × e =x
3 ( x -2 ) · ( e -2 ) + 2 = x
3( x -2 ) · ( e- 2 ) = x -2
din 3 ( e - 2 ) =1 ; e -2 =1 /3 ; e = 2 + 1/3 = 7 / 3
simetric x × x ' = e
3 ( x - 2 ) · ( x ' -2 ) + 2 = 7/3
3 · ( x -2 ) · ( x ' - 2 ) = 7/3 -2 = 1/3
x ' -2 = 1 / 9 ( x -2 ) daca x -2 ≠ 0 ; x ≠ 2
x ' = 2 + 1 / 9(x -2 )