Question

(Z; *steluta) -lege interna (parte stabila) : 2xy+3x+3y+3
FAST

Answer 1

"se observa ca "
(puteti verifica prin calcul)

x*y=2(x+3/2) (y+3/2)-3/2

Verificare
 2( 2x+3)(2y+3)/(2*2)-3/2= (2x+3)(2y+3)/2-3/2= (4xy+6x+6y+9-3)/2=2xy+3x+3y +3

 
∀x, y∈Z x*y= [(2x+3)(2y+3)-3]/2= (4xy+6x+6y+6)/2=2xy+3x+3y ∈Z, pt ca inmultirera si adunarea sunt legi interne pe Z
 adica proidusul si suma  adioua numere intregi sunt numere intregi