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sistem: x+xy+y=11
x-xy+y=1


sistem: xy+x+y=7
xy-3(x+y)=-9


sistem: xy+x+y=11
x (la a doua)y+xy(la a doua)=30


Răspuns :

1) x+xy+y=11
x+10x+y+y=11
11x+2y=11=>x=1=>y=2
La celelalte se procedeaza la fel, descompunand la fel in baza 10