Question

Реши систему уравнений
1
{2x−y=5
{x−2,5y=15
2
{y+x=−5
{x−y=16
срочно

Answer 1

$\displaystyle\bf\\1)\\\\\left \{ {{2x-y=5} \atop {x-2,5y=15} \ |\cdot(-2)} \right. \\\\\\+\left \{ {{2x-y=5} \atop {-2x+5y=-30}} \right. \\-----------\\4y=-25\\\\y=-6,25\\\\x=15+2,5y=15+2,5\cdot (-6,25)=15-15,625=-0,625\\\\Otvet:(-0,625 \ ; \ -6,25)\\\\\\2)\\\\\left \{ {{y+x=-5} \atop {x-y=16}} \right. \\\\\\+\left \{ {{x+y=-5} \atop {x-y=16}} \right. \\--------\\2x=11\\\\x=5,5\\\\y=-5-x=-5-5,5=-10,5\\\\Otvet:(5,5 \ ; \ -10,5)$