Utilizando escalonamento
1 -3 2 8
2 -7 -1 -9
1 2 -1 -7
L2=L2-2L1
L3=L3-L1
1 -3 2 8
0 -1 -5 -25
0 5 -3 -15
L3=L3+5L2
1 -3 2 8 ==> x- 3*0 +2*5=8 ==> x =8-10=-2
0 -1 -5 -25 ==> -y-5z=-25 ==> y=-5*5+25 =0
0 0 -28 -140 ==> -28z =-140 ==>z= 5
x=-2 , y =0 e z = 5
