Exercitide de mai jos va rog urgemnt ! DAu coroana ! NU raspundeti daca nu stiti

1)
{2x+y=-2 |•3
{x+3y=-1
{6x+3y=-6
{x+3y=-1
___________
"-"
6x-x+3y-3y=-6-(-1)
5x=-5|:5
x+3y=-1
3y=-1-x
3y=-1-(-1)
3y=-1+1
3y=0
2)
{x+2y=1|•3
{3x+y=8
{3x+6y=3
{3x+y=8
__________
"-"
5
5y=-5|:5
3x+y=8
3x=8-y
3x=8-(-1)
3x=8+1
3x=9
x=9/3
7)
{x-y=2→x=2+y
{2x+y=7→2(2+y)+y=7
4+2y+y=7
3y=7-4
3y=3|:3
x=2+y→x=2+1