Question

решите систему уравнения способом подстановки
а) {4x-y-8=0
{x-y+1=0
b) {3(x+4y)-4x=2(2x+y)
{7(x-5y)+6x=3(x+4y)+27

Answer 1

Ответ:

(x;y)

a) (3;4)

b) (-2;-1)

Пошаговое объяснение:

a)

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

b)

$\left \{ {3(x+4y)-4x=2(2x+y)} \atop {7(x-5y)+6x=3(x+4y)+27}} \right. \\\left \{ {3x+12y-4x=4x+2y} \atop {7x-35y+6x=3x+12y+27}} \right. \\\left \{ {-x+12y=4x+2y} \atop {7x-35y+6x-3x-12y-27=0}} \right. \\\left \{ {-5x=-10y} \atop {10x=47y=27}} \right. \\\left \{ {x=2y} \atop {x=4.7y+2.7}} \right. \\\left \{ {x=2y} \atop {2y=4.7y+2.7}} \right. \\\left \{ {x=2y} \atop {-2.7=4.7y-2y}} \right. \\\left \{ {x=2y} \atop {-2.7=4.7y-2y}} \right. \\\left \{ {x=-2} \atop {y=-1}} \right.$