Решите систему уравнений 2(3х+2у)+9=4х+21 2х+10=3-(6х+5у)

 2(3х+2у)+9=4х+21

 2х+10=3-(6х+5у)

2(3х+2у)+9=4х+21

2х+10=3-6х-5у

8х=-5у-7

2(3х+2у)+9=4х+21

х=-0,625у-0,875

6х+4у+9=4х+21

х=-0,625у-0,875

2х + 4у=12

х=-0,625у-0,875

2(-0,625у-0,875) + 4у=12

х=-0,625у-0,875

-1,25у +4у =12+ 1,75

х=-0,625у-0,875

2,75у= 13,75

у= 5

х= -0,625*5-0,875

у=5

х=-4

ответ: (-4;5)

1) 2(3х+2у)+9=4х+21

6x + 4y + 9 - 4x - 21= 0

2x+ 4y - 12 = 0

2(x+2y-6) = 0

x + 2y - 6 = 0

x + 2y = 6

2) 2х+10=3-(6х+5у)

2х + 10 - 3 + 6х + 5у = 0

8x + 5y +7 = 0

8x + 5y = -7

x + 2y = 6  \*(-8)

8x + 5y = -7

-8x - 16y = -48

8x + 5y = -7

-11y = -55

y = 5