Question

реши систему уравнений
4х+у=12
7х+2у=20

Answer 1

$\displaystyle\left \{ {{4x+y=12} \atop {7x+2y=20}} \right. \\\left \{ {{y=12-4x} \atop {7x+2*(12-4x)=20}} \right. \\\left \{ {{y=12-4x} \atop {7x+24-8x=20}} \right. \\\left \{ {{y=12-4x} \atop {7x-8x=20-24}} \right. \\\left \{ {{y=12-4x} \atop {-x=-4}} \right. \\\left \{ {{y=12-4x} \atop {x=4}} \right. \\\left \{ {{y=12-4*4} \atop {x=4}} \right.\\\left \{ {{y=12-16} \atop {x=4}} \right. \\\\\left \{ {{y=-4} \atop {x=4}} \right.$

Answer 2

Рещение и ответ - на фотографии