Question

Resolva o sistema { x − 4y = 5
                                3x + y = 2

Answer 1

 { x − 4y = 5     ==>vezes 3==>3x-12y=15   (i)
 {3x + y = 2  (ii)

(i)-(ii)

-13y=13 ==>y=-1

Usando x-4y=5 ==> x+4=5 ==>x=1

Answer 2

{ x − 4y = 5  
{3x + y = 2

{x=5+4y
{3x+y=2

3*(5+4y)+y=2
15+12y+y=2
13y=2-15
13y= -13
y= -13//13
y= -1

3x-1=2

3x=2+1

3x=3

x=3/3

x=1

s ( 1, -1 )