Explicação passo a passo:

1x + 1y + 2z = 9 >>>>>>>>>>>>>>1

2x + 4y – 3z = 1>>>>>>>>>>>>>>>2

3x + 6y – 5z = 0>>>>>>>>>>>>>>3

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CALCULANDO >>>>>>>>>>>>>>>1 E >>>>>>>>>>2

1x + 1y + 2z = 9 >>>>>>>>>>>1 ( VEZES - 2)

2x + 4y – 3z = 1 >>>>>>>>>>> 2

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- 2X - 2Y -4Z = - 18

2X + 4Y - 3Z = 1

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// 2Y - 7Z = -17 >>>>>>>>>>4

CALCULANDO A >>>>>2 COM A >>>>>>3

2x + 4y – 3z = 1>>>>>>>>>>>>>>>2 ( VEZES -3 )

3x + 6y – 5z = 0>>>>>>>>>>>>>>3 ( VEZES 2 )

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- 6X - 12Y + 9Z = - 3>>>>>>>>>>>2

6X + 12Y - 10Z = 0 >>>>>>>>>>3

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// // - Z = - 3

Z = 3 >>>>>>>>>RESPOSTA

EM>>>>>>>>>>>>4 ACIMA SUBSTITUIR Z POR 3

2Y - 7Z = - 17

2Y - 7 * 3 = - 17

2Y - 21 =- 17

2Y = -17 + 21

2Y = +4

Y = 4/2 = 2 >>>>>>RESPOSTA

SUBSTITUINDO EM >>>>>>1 OS VALORES DE Y POR 2 E Z POR 3

X + Y + 2Z = 9

X + 2 + 2 ( 3 ) = 9

X +2 + 6 = 9

X + 8 = 9

X = 9 - 8

X = 1 >>>>>>RESPOSTA