Question

resolva o metodo da adição
a)3x+3y=144
x - 3y = 16

b)2x - y = 5
2 x + y = 15

c) x +3y= 15
- x +2y =10

d) x+ y =10
x-y =20

e) x - 2y =16
x+ 2y = 20

Answer 1

a)
3x + 3y = 144
x - 3y = 16   (+)
---------------------------
4x = 160
x = 160/4
x = 40

x - 3y = 16
40 - 3y = 16
40 - 16 = 3y
24 = 3y
3y = 24
y = 24/3
y = 8

****************************
b)
2x - y = 5
2x + y = 15 (+)
---------------------------
4x = 20
x = 20/4
x = 5

2x - y = 5
2.5 - y = 5
10 - y = 5
10 - 5 = y
5 = y
y = 5

¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨
c)
  x + 3y = 15
- x + 2y = 10  (+)
----------------------
        5y = 25
    y = 25/5
    y = 5

x + 3y = 15
x + 3.5 = 15
x + 15 = 15
x = 15 - 15
x = 0

*****************************
d)
x+ y =10
x - y = 20  (+)
--------------------
2x = 30
x = 30/2
x = 15

x + y = 10
15 + y = 10
y = 10 - 15
y = - 5

*****************************
e)
x - 2y = 16
x + 2y = 20  (+)
--------------------
2x = 36
x = 36/2
x = 18

x + 2y = 20
18 + 2y = 20
2y = 20 - 18
2y = 2
y = 2/2
y = 1