Question

нужны ответы мне ладно

Answer 1

дивіться фото..................

Answer 2

1. Ответ: x=5 ; y=-1

$\left \{ {{2x + y = 9 \: \: | \times 5} \atop {3x - 5y = 20 \: \: \: \: }} \right. \\ \\ \left \{ {{10x + 5y = 45} \atop {3x - 5y = 20}} \right. + \\ 13x = 65 \\ x = 5 \\ \\ 2x + y = 9 \\ 2 \times 5 + y = 9 \\ 10 + y = 9 \\ y = - 1$

2. Ответ: x=2 ; y=-3

$\left \{ {{3x - 4y = 18 \: \: \: \: \: \: } \atop {5x + 2y = 4 \: \: | \times 2 }} \right. \\ \\ \left \{ {{3x - 4y = 18} \atop {10x + 4y = 8}} \right. + \\ 13x = 26 \\ x = 2 \\ \\ 5x + 2y = 4 \\ 5 \times 2 + 2y = 4 \\ 10 + 2y = 4 \\ 2y = - 6$

$\: \: \: \: \: \: \: \: \: \: \: \: \: y = - 3$

3. Ответ: x=1 ; y=3

$\left \{ {{x + 2y = 7 \: \: \: \: \: \: \: \: \: \: \: } \atop {5x - y = 2 \: \: | \times 2}} \right. \\ \\ \left \{ {{x + 2y = 7} \atop {10 - 2y = 4}} \right. + \\ 11x = 11 \\ x = 1 \\ \\ x + 2y = 7 \\ 1 + 2y = 7 \\ 2y = 6 \\ y = 3$

4. Ответ: x=14,5 ; y=-3

$\left \{ {{2x + 5y = 14 \: \: \: \: \: | \times 2 } \atop {3x - 2y = - 17 \: \: | \times 5}} \right. \\ \\ \left \{ {{4x + 10y = 28} \atop {15x - 10y = - 85}} \right. + \\ 19x = - 57 \\ y = - 3 \\ \\ 2x + 5y = 14 \\ 2x + 5 \times ( - 3) = 14 \\ 2x - 15 = 14 \\ 2x = 29$

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: x = 14.5$