Question

(CFTSC) No sistema
{x + 2y = –3
2x – y = 4
o valor de x + y será igual a:

Answer 1

X+2y=-3
2x-y=4 (2)

X+2y=-3
4x-2y=8
5x=5
X=5/5
X=1


1+2y=-3
2y=-3-1
2y=-4/2
Y=-2



X+y -2+1=-1

Answer 2

$Ola'! \\ \\ Temos~duas~equac\~oes: \\ \begin{cases}x+2y=-3~--\ \textgreater \ (I) \\ 2x-y=4~---\ \textgreater \ (II)\end{cases} \\ Na~equac\~ao~(II)~vamos~multiplicar~por~(2)~seria: \\ 2[2x-y=4] \\ 4x-2y=8~---\ \textgreater \ (III) \\ \\ Para~eliminar~a~''y''~vamos~somar~(III)+(I)~assim: \\ +\begin{cases}~~x+2y=-3 \\ \underline{~4x-2y=8~} \\ 5x=5~=\ \textgreater \ \boxed{x=1}\end{cases} \\ \\ pronto~ja~temos~valor~de~''x''~agora~vamos~substituir~em~(I)~ou~(II) \\ observe: \\ Vou~substituir~em~(I)~: \\ 1+2y=-3 \\ 2y=-4 \\ \boxed{y=-2} \\ \\ isso ~ai~ok?$
$Agora~vamos~pede~x+y \\ \\ x+y=1-2 \\ \\ \boxed{\boxed{x+y=-1}}~--\ \textgreater \ terminamos.$