Question

Preciso urgente da resolução dos sistemas de equações:
x+y=11
x-y=3

x-y=1
x+y=4

x-y=16
x+y=74

2x-y=20
2x+y=48

Answer 1

Método da adição (em todos):

a)
x + y = 11
x - y = 3     (+)
---------------
2x = 14
x = 14/2
x = 7

x + y = 11
7 + y = 11
y =  11 - 7
y = 4

*****************************
b)

x - y = 1
x + y = 4  (+)
----------------
2x = 5
x = 5/2

x + y = 4
  5  +  y = 4
-----
  2

5 + 2y =   8
---------   -----
    2          2

5 + 2y = 8
2y = 8 - 5
2y = 3
y = 3/2

**********************
c)

x - y = 16
x + y = 74 (+)
-----------------
2x = 90
x = 90/2
x = 45

x + y = 74
45 + y = 74
y = 74 - 45
y = 29

¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨
d)

2x - y = 20
2x + y = 48  (+)
-------------------
4x = 68
x = 68/4
x = 17

2x + y = 48
2.17 + y = 48
34 + y = 48
y = 48 - 34
y = 14

Answer 2

x+y=11
x-y=3
----------
2x= 14
x= 14/2
x= 7

x+y= 11
7+y= 11
y= 11-7
y= 4
******************
x-y=1
x+y=4
----------
2x=5
x= 5/2
x= 2,5

x+y= 4
2,5+y= 4
y= 4 -2,5
y= 1,5 ou 3/2
*******************
x-y=16
x+y=74
------------
2x=90
x= 90/2
x= 45

x+y= 74
45+y= 74
y= 74 -45
y= 29
****************
2x-y=20
2x+y=48
-------------
4x=68
x= 68/4
x=17

2x+y=48
2×17+y=48
34+y= 48
y= 48-34
y= 14