Question

помогите решить систему линейных уровнений методом сложения умоляю ​

Answer 1

$\displaystyle 1)\left \{ {{7x-4y=11} \atop {3x+12y=-9}} \right.\\ \\3(7x-4y)+(3x+12y)=3*11-9\\24x=24\\x=1\\7*1-4y=11\\y=-1\\(x,y)=(1,-1)\\\\2)\left \{ {{-3x+5y=8} \atop {6x+y=-5}} \right. \\\\(-3x+5y)-5(6x+y)=8-5*(-5)\\-33x=33\\x=-1\\-3(-1)+5y=8\\y=1\\(x,y)=(-1,1)$

Answer 2

$\displaystyle\bf\\1)\\\\\left \{ {{7x-4y=11} \ |\cdot 3 \atop {3x+12y=-9}} \right. \\\\\\+\left \{ {{21x-12y=33} \atop {3x+12y=-9}} \right. \\----------\\24x=24\\\\x=1\\\\4y=7x-11=7\cdot 1-11=7-11=-4\\\\y=-4:4=-1\\\\Otvet: \ (1 \ ; \ -1)$

$\displaystyle\bf\\2)\\\\\left \{ {{-3x+5y=8} \ |\cdot 2 \atop {6x+y=-5}} \right. \\\\\\+\left \{ {{-6x+10y=16} \atop {6x+y=-5}} \right. \\-----------\\11y=11\\\\y=1\\\\6x=-y-5=-1-5=-6\\\\x=-6:6=-1\\\\Otvet: \ (-1 \ ; \ 1)$