Question

решите систему уравнения 3х+2у=5
х+5у=-7

Answer 1

{3х+2у=5
{х+5у=-7     /х(-3)
{3х+2у=5
{-3х-15у=21
-13у=26
у=-2
х-10=-7
х=3

Answer 2

$left { {{3x+2y=5} atop {x+5y=-7}} right.$⇒$left { {{3x+2y=5} atop {x=-7-5y}} right.$
$3(-7-5y)+2y=5$
$-21-15y+2y-5=0$
$-13y=26$
$y=-2$
$x=-7-5y=-7-5*(-2)=3$
ответ: (3;-2)