Question

Помогите решить систему уравнений всеми способами x-y-4=0 3x+y-8=0

Answer 1

1) Способ сложения :

$\left \{ {{x-y-4=0} \atop {3x+y-8=0}} \right.\\\\+\left \{ {{x-y=4} \atop {3x+y=8}} \right. \\------\\4x=12\\\\x=3\\\\y=x-4=3-4=-1\\\\Otvet:\boxed{(3;-1)}$

2) Способ подстановки :

$\left \{ {{x-y-4=0} \atop {3x+y-8=0}} \right.\\\\\left \{ {{x-y=4} \atop {3x+y=8}} \right.\\\\\left \{ {{y=x-4} \atop {3x+x-4=8}} \right.\\\\\left \{ {{y=x-4} \atop {4x=12}} \right. \\\\\left \{ {{x=3} \atop {y=3-4}} \right.\\\\\left \{ {{x=3} \atop {y=-1}} \right.\\\\Otvet:\boxed{(3;-1)}$

3) Решение графически :