Question

Найти ришение примера .Даю 60 балов​

Answer 1

1) В

$\displaystyle\bf\\\left \{ {{x - y = 2 \: \: | \times ( - 3) } \atop {2x - 3y = 5 }} \right. \\ \displaystyle\bf\\ + \left \{ {{ - 3x + 3y = - 6} \atop {2x - 3y = 5 }} \right. \\ \\ - 3x + 2x = - 6 + 5 \\ - x = - 1 \\ x = 1 \\ \\ 1 - y = 2 \\ y = 1 - 2 \\ y = - 1$

Ответ: ( 1 ; - 1 )

2) А

$\displaystyle\bf\\\left \{ {{x + y = 2 \: \: | \times ( - 2) } \atop {5x + 2y = 1 }} \right. \\ \displaystyle\bf\\ + \left \{ {{ - 2x - 2y = - 4} \atop {5x + 2y = 1 }} \right. \\ \\ 5x - 2x = - 4 + 1 \\ 3x = - 3 \\ x = - 3 \div 3 \\ x = - 1 \\ \\ - 1 + y = 2 \\ y = 2 + 1 \\ y = 3$

Ответ: ( - 1 ; 3 )

3) Б

$\displaystyle\bf\\\left \{ {{2x - y = 5 \: \: | \times ( - 1)} \atop {2x + 3y = - 7 }} \right. \\ \displaystyle\bf\\ + \left \{ {{ - 2x + y = - 5} \atop {2x + 3y = - 7 }} \right. \\ \\ y + 3y = - 5 - 7 \\ 4y = - 12 \\ y = - 12 \div 4 \\ y = - 3 \\ \\ 2x - ( - 3) = 5 \\ 2x + 3 = 5 \\ 2x = 5 - 3 \\2 x = 2 \\ x = 2 \div 2 \\ x = 1$

Ответ: ( 1 ; - 3 )