Question

resolva pelo método da adição

$- 5x + y = - 20 \\ 4x - y = 30$


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Answer 1

$\left \{ {{-5x+y=-20} \atop {4x-y=30}} \right.$

$(-5x+y)+(4x-y)=-20+30$

$-5x+y+4x-y=10$

$-x=10$

$x=-10$

$-5x+y=-20$

$-5\cdot (-10)+y=-20$

$50+y=-20$

$y=-20-50$

$y=-70$