Respostas

2014-05-27T14:35:56-03:00
X-2y=10
x+3y=-10
x=2y+10

2y+10+3y=-10
5y=-10-10
5y=-20
y=-20/5
y=-4

x=2.(-4)+10
x=-8+10
x=2

2-2.(-4)=10
2+8=10
2+3.(-4)=-10
2-12=-10

x+y
2-4=-2
1 3 1
2014-05-27T14:36:15-03:00
X-2y=10
x = 10 + 2y

substituindo na equação x + 3y = -10 o valor de x teremos
10 + 2y + 3y = -10
5 y + 10 = -10
5 y = -20
y = -20/5
y = -4

e x = 10 +2y
x = 10 +(-4)
x = 2

então x + y =   2 + (-4) = -2