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If the system of equations ( λ – 1)x + ( λ – 4)y + λ z = 5 λ x + ( λ – 1)y + ( λ –4)z = 7 ( λ + 1)x + ( λ + 2)y – ( λ + 2)z = 9 has infinitely many solutions, then λ 2 + λ is equal to

1. 10
2. 12
3. 6
4. 20

Correct answer: 12

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