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pretty_pretty_piglet


chieu lan luot 3 buc xa co bc song theo ti le =3:4:5 vao catot cua 1 te bao quang dien thi nhan dc cac e co van toc ban dau max tuong ung ti le = 3:k:1 . Trong do k=?
A can 3 B can 2 C 2 D can5
A can 3 B can 2 C 2 D can5