Câu hỏi của Lê Thị Quỳnh Hương

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HT2k02 · Accepted Answer

$\dfrac{5}{2\cdot4}+\dfrac{5}{4\cdot6}+...+\dfrac{5}{48\cdot50}\
=\dfrac{5}{2}\left(\dfrac{2}{2\cdot4}+\dfrac{2}{4\cdot6}+...+\dfrac{2}{48\cdot50}\right)\
=\dfrac{5}{2}\left(\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{6}+...+\dfrac{1}{48}-\dfrac{1}{50}\right)\
=\dfrac{5}{2}\left(\dfrac{1}{2}-\dfrac{1}{50}\right)=\dfrac{5}{2}\cdot\dfrac{12}{25}=\dfrac{6}{5}$Câu trả lời: $\dfrac{5}{2\cdot4}+\dfrac{5}{4\cdot6}+...+\dfrac{5}{48\cdot50}\
=\dfrac{5}{2}\left(\dfrac{2}{2\cdot4}+\dfrac{2}{4\cdot6}+...+\dfrac{2}{48\cdot50}\right)\
=\dfrac{5}{2}\left(\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{6}+...+\dfrac{1}{48}-\dfrac{1}{50}\right)\
=\dfrac{5}{2}\left(\dfrac{1}{2}-\dfrac{1}{50}\right)=\dfrac{5}{2}\cdot\dfrac{12}{25}=\dfrac{6}{5}$

Nguyễn Lê Phước Thịnh · Answer

Ta có: $\dfrac{5}{2\cdot4}+\dfrac{5}{4\cdot6}+...+\dfrac{5}{48\cdot50}$$=\dfrac{5}{2}\cdot\left(\dfrac{2}{2\cdot4}+\dfrac{2}{4\cdot6}+...+\dfrac{2}{48\cdot50}\right)$$=\dfrac{5}{2}\left(\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{6}+...+\dfrac{1}{48}-\dfrac{1}{50}\right)$$=\dfrac{5}{2}\left(\dfrac{1}{2}-\dfrac{1}{50}\right)$$=\dfrac{5}{2}\cdot\dfrac{12}{25}$$=\dfrac{60}{50}=\dfrac{6}{5}$Câu trả lời: Ta có: $\dfrac{5}{2\cdot4}+\dfrac{5}{4\cdot6}+...+\dfrac{5}{48\cdot50}$$=\dfrac{5}{2}\cdot\left(\dfrac{2}{2\cdot4}+\dfrac{2}{4\cdot6}+...+\dfrac{2}{48\cdot50}\right)$$=\dfrac{5}{2}\left(\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{6}+...+\dfrac{1}{48}-\dfrac{1}{50}\right)$$=\dfrac{5}{2}\left(\dfrac{1}{2}-\dfrac{1}{50}\right)$$=\dfrac{5}{2}\cdot\dfrac{12}{25}$$=\dfrac{60}{50}=\dfrac{6}{5}$

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