Question

\(\frac{1}{1.3}+\frac{1}{2.4}+\frac{1}{3.5}+......+\frac{1}{8.10}\)

Ai giải nđúng mk tick nha! Cần gấp trước 6h

Answer 1

\(\frac{1}{1.3}+\frac{1}{2.4}+\frac{1}{3.5}+.....+\frac{1}{8.10}\)

\(=\left(\frac{1}{1.3}+\frac{1}{3.5}+....+\frac{1}{7.9}\right)+\left(\frac{1}{2.4}+\frac{1}{4.6}+.....+\frac{1}{8.10}\right)\)

\(=\frac{1}{2}\left(1-\frac{1}{3}+...+\frac{1}{7}-\frac{1}{9}\right)+\frac{1}{2}\left(\frac{1}{2}-\frac{1}{4}+...+\frac{1}{8}-\frac{1}{10}\right)\)

\(=\frac{1}{2}\left(1-\frac{1}{9}\right)+\frac{1}{2}\left(\frac{1}{2}-\frac{1}{10}\right)\)

\(=\frac{1}{2}\cdot\frac{8}{9}+\frac{1}{2}\cdot\frac{2}{5}=\frac{4}{9}+\frac{1}{5}=\frac{29}{45}\)

Answer 2

=1/2x(1-1/3+1/2-1/4+1/3-1/5+1/4-1/6+.....+1/8-1/10)

=1/2x58/45

=29/45

Answer 3

Kết quả bằng 29/45

Bạn k cho mình nha

Answer 4

kết quả là 29/45 nha 

Answer 5

Bài làm:

\(\left(\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{7.9}\right)+\left(\frac{1}{2.4}+\frac{1}{4.6}+...+\frac{1}{8.10}\right)\)

\(=\frac{1}{2}\left(1-\frac{1}{9}\right)+\frac{1}{2}\left(\frac{1}{2}-\frac{1}{10}\right)\)

\(=\frac{1}{2}.\frac{8}{9}+\frac{1}{2}.\frac{2}{5}=\frac{4}{9}+\frac{1}{5}=\frac{29}{45}\)