Question

x-4y=10
2y+x=20



x+y=9
2x-9y=3

Answer 1

a) x=10+4y

2y + 10 + 4y = 20 ou 6y = 10 que dá y=10/6  então y = 5/3

x=10+4(5/3) então x=10 + 20/3 tirando MMC x= (30+20)/3

x=50/3

50/3=10+4(5/3)

50/3=10+20/3

50/3=50/3

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b) x=9-y

2(9-y)-9y=3

18-2y-9y=3

-11y=3-18 então -11y = -15 ou y=-15/-11 (-1) y=15/11

x=9-15/11 então com MMC x= 99-15/11 então x=84/11

Se x=9-y  então 84/11 = 9-(15/11) (MMC) 84/11 = 84/11

Answer 2

X - 4y=10

2y + x=20

x - 4y = 10

x + 2y = 20 .(2)

x - 4y = 10

2x + 4y = 40 (+)

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3x = 50

x = 50/3

x - 4y = 10

50/3 - 4y = 10

50/3 - 10 = 4y

(50 - 3.10)/3 = 3.4y/3

50 - 30 = 12y

20 = 12y

12y = 20

y = 20/12 (:4)/(:4)

y = 5/3

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x + y = 9 (-2)

2x-9y = 3

- 2x - 2y = - 18

2x - 9y = 3 (+)

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- 11y = - 15

11y = 15

y = 15/11

x + y = 9

x + 15/11 = 9

x = 9 - 15/11

11x/11 = (11.9 - 15)/11

11x = 99 - 15

11x = 84

x = 84/11