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Tìm tất cả số nguyên dương n sao cho A= n.4^n + 3^n chia hết cho 7

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Với `n` là số chẵn `n = 2k` thì `:`

`A = 2k . 4^{2k} + 3^{2k} = ( 2k + 1 ) . 4^{2k} + ( 16^k - 9^k ) ⋮ 7 ⇒ 2k + 1 ⋮ 7 ⇒ k = {7t - 1} / 2 ⇒ n = 14t - 1 = 14m + 6 ( m ∈ NN )`

Với `n` là số lẻ `n = 2k + 1` thì `:`

`A = ( 2k + 1 ) . 4^{2k + 1} + 3^{2k + 1} = 2k . 4^{2k + 1} + ( 4^{2k + 1} + 3^{2k + 1} ) ⋮ 7 ⇒ 2k ⋮ 7 ⇒ k = 7t ⇒ n = 14m + 1 ( m ∈ NN )`

Vậy `n = 14m + 6` hoặc `n = 14m + 1` `(` với `AA n ∈ NN` `)` thì `A ⋮ 7`

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Choose the best answer.
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Choose the best answer.
I think that ______ cauliflower is not enough for 3 people. Let’s buy one more.

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Tìm tất cả số nguyên dương n sao cho A= n.4^n + 3^n chia hết cho 7

1 câu trả lời

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Choose the best answer.I think you should buy _____ pack of mineral water instead. And you can also buy _____ snacks such as potato crisps, 3 kilos of mandarins, 2 kilos of apples, 3 bunches of bananas, ______ cookies and soft candies.

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Choose the best answer.I think that ______ cauliflower is not enough for 3 people. Let’s buy one more.

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I think you should buy ___ pack of mineral water instead. And you can also buy _ snacks such as potato crisps, 3 kilos of mandarins, 2 kilos of apples, 3 bunches of bananas, ____ cookies and soft candies.

Choose the best answer.
We should decorate our living room with _ orange banner. We also need ____ ribbons, balloons, party hats and costume.

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