Question

[Edogawa Conan]

\(\frac{12}{1.4}+\frac{12}{4.7}+\frac{12}{7.10}+......+\frac{12}{97.100}\)

bạn nào biết giải 2 cách càng tốt

ths nhìu

Answer 1

[Hoàng Phúc]

\(\frac{12}{1.4}+\frac{12}{4.7}+\frac{12}{7.10}+...+\frac{12}{97.100}\)

\(=\frac{12}{3}.\left(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{97.100}\right)\)

\(=4.\left(\frac{1}{1}-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{97}-\frac{1}{100}\right)\)

\(=4.\left(1-\frac{1}{100}\right)=4.\frac{99}{100}=\frac{99}{25}\)