Câu hỏi của Nguyễn Huy Hoàng

Question

( 1/2x4+1/4 x 6+1/6x8+....+1/98 x 100) / y = 147/50 tìm y

Nguyễn Lương Bảo Tiên · Accepted Answer

$\frac{\frac{1}{2\times4}+\frac{1}{4\times6}+\frac{1}{6\times8}+...+\frac{1}{98\times100}}{y}=\frac{147}{50}$$\frac{\frac{1}{2}\times\left(\frac{2}{2\times4}+\frac{2}{4\times6}+\frac{2}{6\times8}+...+\frac{2}{98\times100}\right)}{y}=\frac{147}{50}$$\frac{\frac{1}{2}\times\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{98}-\frac{1}{100}\right)}{y}=\frac{147}{50}$$\frac{\frac{1}{2}\times\left(\frac{1}{2}-\frac{1}{100}\right)}{y}=\frac{147}{50}$$\frac{\frac{1}{2}\times\frac{49}{100}}{y}=\frac{147}{50}$$\frac{49}{200}:y=\frac{147}{50}$$y=\frac{49}{200}:\frac{147}{50}$$y=\frac{1}{12}$Câu trả lời: $\frac{\frac{1}{2\times4}+\frac{1}{4\times6}+\frac{1}{6\times8}+...+\frac{1}{98\times100}}{y}=\frac{147}{50}$$\frac{\frac{1}{2}\times\left(\frac{2}{2\times4}+\frac{2}{4\times6}+\frac{2}{6\times8}+...+\frac{2}{98\times100}\right)}{y}=\frac{147}{50}$$\frac{\frac{1}{2}\times\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{98}-\frac{1}{100}\right)}{y}=\frac{147}{50}$$\frac{\frac{1}{2}\times\left(\frac{1}{2}-\frac{1}{100}\right)}{y}=\frac{147}{50}$$\frac{\frac{1}{2}\times\frac{49}{100}}{y}=\frac{147}{50}$$\frac{49}{200}:y=\frac{147}{50}$$y=\frac{49}{200}:\frac{147}{50}$$y=\frac{1}{12}$

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