Question

розв'яжіть систему рівнянь способом підстановки x-2y=1 3x+y=-4​

Answer 1

Ответ:

(-1; -1)

Объяснение:

x-2y=1

3x+y=-4​

х=2у+1

3(2у+1)+у=-4

х=2у+1

6у+3+у=-4

х=2у+1

7у=-7;  у=-1

х=-1*2+1=-1

у=-1

Answer 2

$\displaystyle\bf\\\left \{ {{x-2y=1} \atop {3x+y=-4}} \right.\\\\\\\left \{ {{x=2y+1} \atop {3\cdot(2y+1)+y=-4}} \right.\\\\\\\left \{ {{x=2y+1} \atop {6y+3+y=-4}} \right.\\\\\\\left \{ {{x=2y+1} \atop {7y=-7}} \right. \\\\\\\left \{ {{x=2\cdot(-1)+1} \atop {y=-1}} \right.\\\\\\\left \{ {{x=-1} \atop {y=-1}} \right. \\\\\\Otvet \ : \ \Big(-1 \ ; \ -1\Big)$