Question

[Đỗ Anh Duy]

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Answer 1

[l҉o҉n҉g҉ d҉z҉]

Từ a + b + c = 0 => ( a + b + c )² = 0 

<=> a² + b² + c² + 2ab + 2bc + 2ca = 0

<=> ab + bc + ca = -7

=> ( ab + bc + ca )² = 49

<=> a²b² + b²c² + c²a² + 2ab²c + 2bc²a + 2a²bc = 49

<=> a²b² + b²c² + c²a² + 2abc( a + b + c ) = 49

<=> a²b² + b²c² + c²a² = 49 ( vì a + b + c = 0 )

Từ a² + b² + c² = 14 => ( a² + b² + c² )² = 196

<=> a⁴ + b⁴ + c⁴ + 2a²b² + 2b²c² + 2c²a² = 196

<=> a⁴ + b⁴ + c⁴ = 98