How do you solve $x + y = -4$ and $y = -3x + 2$ using substitution?

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Answer 1 · 2017-07-12T17:51:58

$(x,y)=(-3,-7)$

$x+y=-4--(1)$

$y=-3x+2--(2)$

substitute for y from $(2)" "$ into $" "(1)$

$x+ -3x+2=-4$

$-2x=-4-2$

$=>x=3$

substitute into $(1)$ to find $y$
https://socratic.org/
$3+y=-4$

$=>y=-7$

$:.(x,y)=(3,-7)$

a quick mental check for $eqn(2)$ will see that the solution is consistent.

How do you solve x + y = -4x + y = -4 and y = -3x + 2y = -3x + 2 using substitution?