Răspuns:
a) R: x = -3 , y = -1
[tex]a)\\2x+y=-7 \\ 3x-4y=-5 \\Inmultim \ prima \ ecuatie \ cu \ 4=>\\8x+4y=-28\\3x-4y=-5\\Adunam \ ecuatiile \ => 11x=-33 => x= -3\\Inlocuim \ cu \ valoare \ lui \ x \ in \ prima \ ecuatie \ si \ rezulta =>\\-6+y=-7 =>y=-1[/tex]
b)R: x = -4 , y = 2
[tex]x-2y=-8\\3x+4y=-4\\Inmultim \ cu \ 2 \ prima \ ecuatie =>\\2x -4y=-16\\3x+4y=-4\\Adunam => 5x=-20 => x=-4\\In \ prima \ ecuatie => -4 -2y=-8 => -2y =-4 => y=2[/tex]
c) R: x = 3, y = -4
[tex]x+y=-1\\5x+2y=7\\Inmultim \ cu \ -2 \ prima \ ecuatie =>\\-2x-2y=2\\5x+2y=7\\Adunam => 3x=9 => x=3\\3+y=-1 => y=-4[/tex]
d) R: x = -3, y = 4
[tex]2x+y=-2\\4x+5y=8\\Inmultim \ cu \ -2 \ prima \ ecuatie:\\-4x -2y =4\\4x+5y=8\\Adunam =>\\3y=12 => y=4\\2x+4=-2 => 2x=-6 => x=-3[/tex]
