ĐẶT AB A AC B AD C               ,                ,  , GỌI M LÀ TRUNG ĐIỂM CỦA BC

Câu 64: Cho tứ diện ABCD. Đặt

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AB a AC b AD c

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gọi M là trung điểm của BC. Trong các

khẳng định sau, khẳng định nào đúng?

B.

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^DM

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^{a b c}

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A.

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¹

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^{a b}

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C.

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D.

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