Verified answer

1) а)

[tex]\displaystyle\bf\\\left \{ {{2x - y = 2 \: \: | \times 2} \atop {x + 2y = - 4 }} \right. \\ \displaystyle\bf\\ + \left \{ {{4x - 2y = 4} \atop {x + 2y = - 4 }} \right. \\ \\ 4x + x = 4 - 4 \\ 5x = 0 \\ x = 0 \\ \\ 2 \times 0 - y = 2 \\ - y = 2 \\ y = - 2[/tex]

Ответ: ( 0 ; - 2 )

2) б)

[tex]\displaystyle\bf\\\left \{ {{ - 2x + 5y = 14} \atop {x + 2y = - 6 \: \: | \times 2}} \right. \\ \displaystyle\bf\\ + \left \{ {{ - 2x + 5y = 14} \atop {2x + 4y = - 12 }} \right. \\ \\ 2x - 2x + 5y + 4y = 14 - 12 \\ 0 + 9y = 2[/tex]

3) а)

[tex]\displaystyle\bf\\\left \{ {{3x - 2y = 4} \atop {4x + y = - 6 }} \right. \\ \displaystyle\bf\\\left \{ {{3x - 2( - 6 - 4x) = 4} \atop {y = - 6 - 4x }} \right. \\ \\ [/tex]