Question

\(C=\frac{2}{1.4}+\frac{2}{4.7}+\frac{2}{7.10}+.....+\frac{2}{601.604}\)tính 

Answer 1

C = 2/1.4 + 2/4.7 + 2/7.10 + .... + 2/601.604

C = 2/3 . ( 3/1.4 + 3/4.7 + 3/7.10 + ... + 3/601.604 )

C = 2/3 . ( 1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + ... + 1/601 - 1/604 )

C = 2/3 . ( 1 - 1/604 )

C = 2/3 . 603/604

C = 201/302

Answer 2

\(C=\frac{2}{1.4}+\frac{2}{4.7}+\frac{2}{7.10}+.....+\frac{2}{601.604}=\frac{2}{3}\cdot\left(\frac{3}{1.4}+\frac{3}{4.7}+...+\frac{3}{601.604}\right)=\frac{2}{3}\cdot\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+...+\frac{1}{601}-\frac{1}{604}\right)\)=\(\frac{2}{3}\cdot\left(1-\frac{1}{604}\right)=\frac{2}{3}\cdot\frac{603}{604}=\frac{201}{302}\)