1.
[tex]3x + y = 7 \\ 2x + 5y = 9 \\ y = 7 - 3x \\ 2x + 5(7 - 3x) = 9 \\ 2x + 35 - 15x = 9 \\ 2x - 15x = 9 - 35 \\ - 13x = - 26 \\ x = 2 \\ y = 7 - 3 \times 2 \\ y = 1 \\ sprawdzenie \\ 3 \times 2 + 1 = 7 \\ 2 \times 2 + 5 = 9 \\ 7 = 7 \\ 9 = 9[/tex]
2.
[tex]x + 2y = 3 \\ 3x - y = - 5 \\ x = 3 - 2y \\ 3(3 - 2y) - y = - 5 \\ 9 - 6y - y = - 5 \\ - 7y = - 14 \\ y = 2 \\ x = 3 - 2 \times 2 \\ x = - 1 \\ sprawdzenie \\ - 1 + 2 \times 2 = 3 \\ 3 \times ( - 1) - 2 = - 5 \\ 3 = 3 \\ - 5 = - 5[/tex]