Question

\(C=\frac{2}{1.4}+\frac{2}{4.7}+\frac{2}{7.10}+....+\frac{2}{37.40}\)

Answer 1

Giải: 

C = \(\frac{2}{1.4}+\frac{2}{4.7}+\frac{2}{7.10}+...+\frac{2}{37.40}\)

C = \(2\left(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{37.40}\right)\)

C = \(2\left(\frac{1}{1}-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{37}-\frac{1}{40}\right)\)

C = \(2\left(\frac{1}{1}-\frac{1}{40}\right)\)

C = \(2.\frac{39}{40}\)

C = \(\frac{39}{20}\)

Answer 2

C=2(\(\frac{1}{1.4}+\frac{1}{4.7}+...+\frac{1}{37.40}\))

   =2.1/3(\(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+...+\frac{1}{37}-\frac{1}{40}\))

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