a/b=2/7(relatia 1)
a-b=50(relatia 2)
a*b=?
(2)=>a=50+b
(1)=>7a=2b=>7(50+b)=2b
350+7b=2b
5b=-350
b=-70
Inlocuind in relatia 2 obtinem ca a=50-70
a=-20
Proba: -20/-70=2/7 simplificam prin 10 prima fractie si stim ca - impartit la - face + =>2/7=2/7 adevarat
Produsul, P=a*b=-20*(-70)=1400
