Question

8 (2 бали). Розв'яжіть систему рівнянь [3(4x-5)-4(7-3y) = -19, (5(6y-4)-(5+7x) = -2. 3) 8​

Answer 1

$\displaystyle\bf\\\left \{ {{3(4x-5)-4(7-3y)=-19} \atop {5(6y-4)-(5+7x)=-2}} \right. \\\\\\\left \{ {{12x-15-28+12y=-19} \atop {30y-20-5-7x=-2}} \right. \\\\\\\left \{ {{12x+12y=-19+15+28} \atop {-7x+30y=-2+20+5}} \right. \\\\\\\left \{ {{12x+12y=24} \atop {-7x+30y=23}} \right. \\\\\\\left \{ {{x+y=2} \ |\cdot 7\atop {-7x+30y=23}} \right.\\\\\\+\left \{ {{7x+7y=14} \atop {-7x+30y=23}} \right.\\-----------\\37y=37\\\\y=37:37=1\\\\x=2-y=2-1=1\\\\Otvet \ : \ (1 \ ; \ 1)$

Answer 2

Объяснение:

3(4х - 5) - 4(7 - 3у) = -19

5(6у - 4) - (5 + 7х) = -2

12х - 15 - 28 + 12у = -19

30у - 20 - 5 - 7х = -2

12х + 12у = -19 + 15 + 28

-7х + 30у = -2 + 20 + 5

12х + 12у = 24 | : 12

-7х + 30у = 23

х + у = 2

-7х + 30у = 23

х = 2 - у

-7х + 30у = 23

1)

-7х + 30у = 23

-7(2 - у) + 30у = 23

-14 + 7у + 30у = 23

7у + 30у = 23 + 14

37у = 37

у = 37 : 37

у = 1

2)

х = 2 - у

х = 2 - 1

х = 1

Ответ: (1; 1)