Question

Resolva os sistemas:
A:
4.{x+y/6}=18
2x-y=13

B:
12x-5y=18
y-2/3x= -1

Answer 1

a)

4x + 4y    = 18
        -----
          6

4x +  2y   =  18
        ------
          3

12x + 2y = 54
-----------    ------
      3           3

12x + 2y = 54  (:2)
6x + y = 27

6x + y = 27
2x - y = 13     (+)
---------------------
8x = 40
x = 40/8
x = 5


2x - y = 13
2.5 - y = 13
10 - y = 13
10 - 13 = y
- 3 = y
y  = - 3

¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨
b)

12x - 5y = 18
y -   2   x  =  - 1
      ----
       3

3y - 2x = - 3
---------    ------
    3           3

- 2x + 3y = - 3

12x - 5y = 18
- 2x + 3y = - 3   (6)

12x - 5y = 18
- 12x + 18y = - 18  (+)
-------------------------------
   0    + 13y   =  0

13y = 0
y = 0/13
y = 0

- 2x + 3y = - 3
- 2x + 3.0 = - 3
- 2x + 0 = - 3  (-1)
2x = 3
x = 3/2

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