Question

Пожалуйста помогите решить.
Заранее спасибо.​

Answer 1

$1)\left \{ {{5x+2y=8} \atop {3x-y=7}|*2} \right.\\\\+\left \{ {{5x+2y=8} \atop {6x-2y=14}} \right.\\-------\\11x=22\\x=2\\y=3x-7=3*2-7=-1\\\\Otvet:\boxed{(2;-1)}$

$2)\left \{ {{3x+4y=13} \atop {5x+2y=17}|*(-2)} \right.\\\\+\left \{ {{3x+4y=13} \atop {-10x-4y=-34}} \right.\\---------\\-7x=-21\\x=3\\2y=17-5x=17-5*3=17-15=2\\y=1\\\\Otvet:\boxed{(3;1)}$

$3)\left \{ {{x-y=5} \atop {xy=14}} \right.\\\\\left \{ {{x+(-y)=5} \atop {x*(-y)=-14}} \right.\\\\1)\left \{ {{x=7} \atop {-y=-2}} \right.\\\\\left \{ {{x=7} \atop {y=2}} \right.\\\\2)\left \{ {{x=-2} \atop {-y=7}} \right.\\\\\left \{ {{x=-2} \atop {y=-7}} \right.\\\\Otvet:\boxed{(7;2),(-2;-7)}$