Kham khảo tại link:
Câu hỏi của Lê Thúy Hằng - Toán lớp 6 | Học trực tuyến
https://h.vn/hoi-dap/question/821353.html
\(B=1-\frac{1}{2.5}+1-\frac{1}{5.8}+...+1-\frac{1}{50.53}\)
\(B=17-\frac{1}{3}\left(\frac{3}{2.5}+\frac{3}{5.8}+....+\frac{3}{50.53}\right)\)
\(B=17-\frac{1}{3}\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-.....-\frac{1}{53}\right)\)
\(B=17-\frac{1}{3}\left(\frac{1}{2}-\frac{1}{53}\right)=17-\frac{1}{3}.\frac{51}{106}=17-\frac{17}{106}=17\left(1-\frac{1}{106}\right)=17.\frac{105}{106}=\frac{1785}{106}\)
B=9/2,5+39/5,8+87/8,11+...+2649/50,53
B=2,5-1/2,5+5,8-1/5,8+8,11-1/8,11+...+50,53-1/50,53
B=1-1/2,5+1-1/5,8+1-1/8,11+...+1-1/50,53
B=17-1/3(3/2,5+3/5,8+3/8,11+...+3/50,53
B=17-1/3(1/2-1/5+1/5-1/8+...+1/50-1/53)
B=17-1/3(1/2-1/53)
B=1785/106
Học tốt nha bạn ~!!!
