Aratati ca x compus y= 2(x+3)(y+3)-3
legea este x compus cu y= 2xy+6x+6y+15


Răspuns :

[tex]\\ \boxed{x*y = 2(x+3)(y+3)-3} \\ \\ =\ \textgreater \ 2(xy + 3x + 3y+9) - 3 \\ =\ \textgreater \ 2xy +6x +6y + 18 -3 \\ \\ =\ \textgreater \ \boxed{2xy +6x +6y + 15}[/tex]
Varianta I :
Legea de compozitie :
x ° y = 2xy+6x+6y+15
x ° y =2x(y+3)+6y+18-3
x ° y =2x(y+3)+6(y+3)-3
x ° y =(2x+6)(y+3)-3
x ° y =2(x+3)(y+3)-3


Varianta II :
Avem 
x ° y = 2(x+3)(y+3)-3
x ° y = (2x+6)(y+3)-3
x ° y =2xy+6x+6y+18-3
x ° y =2xy+6x+6y+15  - A