[tex]\underline{Metoda~I} \\ a+b=7,21 \Rightarrow a=7,21-b \\ a-b=2,17 \Leftrightarrow 7,21-b-b=2,17 \Leftrightarrow 7,21-2b=2,17 \Rightarrow \\ \Rightarrow 2b=7,21-2,17 \Rightarrow 2b=5,04 \Rightarrow b=2,52. \\ \\ a=7,21-2,52=4,69. \\ \\ \underline{Solutie}: (a;b)=(4,69~;~2,52).[/tex]
[tex]\underline{Metoda~II} \\ a+b=7,21 \\ a-b=2,17 \\ ------~(adunam) \\ 2a=9,38 \Rightarrow a=4,69. \\ \\ a+b=7,21 \Rightarrow b=7,21-a=7,21-4,69=2,52.[/tex]
