b) [tex]\left \{ {{ -x+y=4 } \atop { 5x+2y=8 }} \right. \iff\left \{ {{ x=-4+y } \atop { 5x+2y=8 }} \right. \\[/tex]
5(-4+y) + 2y = 8
-20 + 5y + 2y = 8
7y = 28
y = 4
x = -4 + y = -4 + 4 = 0
c) [tex]\left \{ {{ -3x+4y=-6 } \atop { 2x+y=4 }} \right. \iff\left \{ {{ -3x+4y=-6 } \atop { y=4-2x }} \right. \\[/tex]
-3x + 4y = -6
-3x + 4(4-2x) = -6
-3x + 16 - 8x = -6
-11x = -22
x = 2
y = 4-2x = 4-4
⇒ y = 0
d) [tex]\left \{ {{ 2x-3y=-3 } \atop { 3x+y=12 }} \right. \iff\left \{ {{ 2x-3y=-3 } \atop { y=12-3x }} \right. \\[/tex]
2x - 3(12-3x) = -3
2x - 36 + 9x = -3
11x = 33
x = 3
2x - 3y = -3
6 - 3y = -3
-3y = -9
y = 3
____________________
Bonus Brainly oferit de @carmentofan despre metoda substituției:
https://brainly.ro/tema/5889017
Succes! ❀
Echipa BrainlyRO
