Question

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

Answer 1

x + y = 4
x - y = 2

2x = 6
x = 3

x + y = 4
3 + y = 4
y = 4 - 3
y = 1

S = { 3 ; 1 }

Answer 2

$\left \{ {{x+y=4} \atop {x-y=2}} \right. \\\\\\ x+y=4\to x=-y+4\\\\\\ x-y=2\to -y+4-y=2\to -y-y=2-4\to -2y=-2\to\\ y= \frac{-2}{-2}\to y=1\\\\\\ x=-y+4\to x=-1+4\to x=3\\\\\\ S= \left \{3;1 \left \}$