Question

Resolva os sistemas lineares pelo o metodo da adição.
A) 3x+4y=2
4x-5y=3

B) 2x+5y=3
x-3y=1

C)x-y=1
x+y=2

Answer 1

A) 3x+4y=2  . (5)

4x-5y=3  . (4)

15x+20y = 10

16x-20y = 12  

______________

31x = 22

x = 22/31

3x+4y=2

3 . 22/31 + 4y = 2

66/31 + 4y = 2

4y = 2 - 66/31

4y = (62 - 66)/31

y = -4/31  . 1/4

y = -4/124

y = -1/31

_____________________________

B) 2x+5y=3  . (3)

x-3y=1  . (5)

6x+15y = 9

5x-15y = 5

__________

11x = 14

x = 14/11

2x+5y=3

2 . 14/11 + 5y = 3

28/11 + 5y = 3

5y = 3 - 28/11

5y = (33 - 28)/11

y = 5/11 . 1/5

y = 1/11

_____________________________

C)x-y=1

x+y=2

______

2x = 3

x = 3/2

x+y=2

3/2 + y = 2

y = 2 - 3/2

y = (4 - 3)/2

y = 1/2