\(\dfrac{6^{25}}{4^{12}.9^{13}}\)

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Câu 1: cho vật A trong 2 phút thực hiện được 3600 dao động.Vật B trong 1 phút thực hiện được 900 dao động.

a)Tính tần số của mỗi vật.Vật nào phát ra âm cao hơn?

b)Tai ta nghe được âm do vật A nào phát ra không?Vì sao?

People find treasures in some very unusual places. Dutch teacher Paul van den Heuval was teaching his class about World War II, so he visited an antique store to look for items from the 1940s. As he was looking at some old postcards, Paul was surprised to find one signed with the name "Anne Frank". At first, van den Hauvel (1).________ that the postcard wasn't real. Some experts examined the postcard carefully. They finally (2).______ that the real Anne Frank had written it. The postcard became very (3)._____ and is (4)._______ worth over 165,000. But perhaps it is really the postcard's historical, rather than (5)._______ , value that is the most important.

People find treasures in some very unusual places. Dutch teacher Paul van den Heuval was teaching his class about World War II, so he visited an antique store to look for items from the 1940s. As he was looking at some old postcards, Paul was surprised to find one signed with the name "Anne Frank". At first, van den Hauvel (1).________ that the postcard wasn't real. Some experts examined the postcard carefully. They finally (2).______ that the real Anne Frank had written it. The postcard became very (3)._____ and is (4)._______ worth over 165,000. But perhaps it is really the postcard's historical, rather than (5)._______ , value that is the most important.

People find treasures in some very unusual places. Dutch teacher Paul van den Heuval was teaching his class about World War II, so he visited an antique store to look for items from the 1940s. As he was looking at some old postcards, Paul was surprised to find one signed with the name "Anne Frank". At first, van den Hauvel (1).________ that the postcard wasn't real. Some experts examined the postcard carefully. They finally (2).______ that the real Anne Frank had written it. The postcard became very (3)._____ and is (4)._______ worth over 165,000. But perhaps it is really the postcard's historical, rather than (5)._______ , value that is the most important.

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