Ответ:

[tex](1; 5); \quad (3; -2);[/tex]

Объяснение:

[tex]3. \quad \displaystyle \left \{ {{y-3x=2} \atop {2y-5x=5}} \right. \Leftrightarrow \left \{ {{3x-y=-2} \atop {2y-5x=5}} \right. \Leftrightarrow \left \{ {{6x-2y=-4} \atop {2y-5x=5}} \right. \bigg |+[/tex]

[tex]6x-2y+2y-5x=-4+5;[/tex]

[tex]x=1;[/tex]

[tex]y-3 \cdot 1=2 \Rightarrow y=3+2=5;[/tex]

[tex](1; 5);[/tex]

[tex]4.\quad \displaystyle \left \{ {{4x+3y=6} \atop {2x+y=4}} \right. \Leftrightarrow \left \{ {{4x+3y=6} \atop {-6x-3y=-12}} \right. \bigg |+[/tex]

[tex]4x+3y-6x-3y=6-12;[/tex]

[tex]-2x=-6;[/tex]

[tex]x=3;[/tex]

[tex]y=4-2 \cdot 3=4-6=-2;[/tex]

[tex](3; -2);[/tex]