Question

resolva os seguintes sistemas pelo método que preferirem
x+3y=5
2x-y=-4

Answer 1

x+3y=5
2x-y=-4 . (3)

x + 3y = 5
6x - 3y = - 12

7x = - 7
x = - 1

x + 3y = 5
- 1 + 3y = 5
3y = 5 + 1
3y = 6
y = 2

S = { - 1 ; 2 }

Answer 2

$\left \{ {{x+3y=5} \atop {2x-y=-4}} \right. \\\\\\ x+3y=5\to x=-3y+5\\\\\\ 2x-y=-4\to2(-3y+5)=-4\to -6y+10-y=-4\to \\\\ -6y-y=-4-10\to -7y=-14\to y= \frac{-14}{-7} \to y=2\\\\\\ x=-3y+5\to x=-3*2+5\to x=-6+5\to x=-1\\\\\\\\ S= \left \{ -1;2 \left \}$