Question

a) 6x + y = 25 (6x - 2y = 10
b)5x - 4y = 15 (6x - 4y =18
c)x - 5y = -7 (5x- 5x = 5
d)x - y =3(x + 3y = 11
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Answer 1

Resposta:

a)

Y = 25-6x ( isolando )

6x - 2( 25-6x) = 10

6x - 50 + 12 x = 10

6x+12x = 10+50

18x = 60

x = 60/18

x = 30 / 9

X = 10/3

6.10/3 + Y = 25

60/3 + Y = 25

20 + Y = 25

Y = 25- 20 = 5

x = 10/3

Y = 5

b)

5x - 4y = 15  

5x = 15 + 4y    

x = (15 + 4y)/5                                                      

6 ( 15 + 4y)/5 - 4y = 18  

(90 + 24y)/ 5  - 4y = 18

90  mmc= 5

(90 + 24 y) - 5. 4y = 5. 18    

90 + 24 y - 20y = 90 corta 90 com 90

24y - 20 y = 0  

y = 0

x = 15 /5 = 3

d)

x-y=3

x+3y=11

x = 3 + y

3+y + 3y = 11

4y= 11-3

4y = 8

y = 8/4

y = 2

x = 3 + y

x = 3 + 2

x = 5