Question

Решите систему уравнений способом подстановки: 1) {8x - 3y = 7 {3x + y = 92) {12x - y = 18 {x + 0,5 y = 5

Answer 1

{Y=9-3x. Y=9-6
{8x-3(9-3x)=7. Y=3
8x-27+9x-7=0
17x=34
X=2


{y=12x-18
{x+0,5y=5
X+0,5(12x-18)=5
X+6x-9=5
7x=14
X=2
Y=12*2-18=6

Answer 2

1) 8x - 3y = 7
   3x + y = 9

8x-3y=7
y=9-3x

8x-3(9-3x)=7
y=9-3x

8x-27+9x=7
y=9-3x

17x=34
y=9-3x

x=2
y=3

2) 12x - y = 18
    x + 0,5 y = 5

12x-y=18
x=5-0.5y

12(5-0.5y)=18
x=5-0.5y

60-6y=18
x=5-0.5y

-6y=-42
x=5-0.5y

y=7
x=5-3.5

y=7
x=1.5