Question

B=1/1.4 + 1/4.7 + 1/7.10 + ... + 1/100.103

Mình đang cần gấp, bạn nào nhanh mình tick cho (nhớ hướng dẫn giải chi tiết nhé)

Thanks, nhớ kết bạn với mình nhé ^_^!!!!!

Answer 1

\(3B=\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{100.103}.\)

\(3B=\frac{4-1}{1.4}+\frac{7-4}{4.7}+\frac{10-7}{7.10}+...+\frac{103-100}{100.103}\)

\(3B=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{100}-\frac{1}{103}=1-\frac{1}{103}=\frac{102}{103}\)

\(B=\frac{102}{3.103}=\frac{34}{103}\)

Answer 2

3B=3/1.4+3/4.7+3/7.10+...+3/100.103 3B=(4-1)/1.4+(7-4)/4.7+(10-7)/7.10+...+(103-100)/100.103 3B=1-1/4+1/4-1/7+1/7-1/10+...+1/100-1/103=1-1/103=102/103 B=102/(3.103)=34/103

Answer 3

B=\(\frac{1}{1.4}+\frac{1}{4.7}+\frac{1}{7.10}+......+\frac{1}{100.103}\)

B=\(\frac{1}{3}.\left(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+....+\frac{3}{100.103}\right)\)

B=\(\frac{1}{3}.\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+......+\frac{1}{100}-\frac{1}{103}\right)\)

B=\(\frac{1}{3}.\left(1-\frac{1}{103}\right)\)

B=\(\frac{1}{3}.\frac{102}{103}\)

B=\(\frac{34}{103}\)

Answer 4

B = 3/1x4 + 3/4x7 + 3/7x10 +.............+ 3/100x103

B = 4-1/1x4 + 7-4/4x7 + 10-7/7x10 + ........... + 103-103/100x103

B = 1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + ..... + 1/100 - 1/103 

B = 1 - 1/103

B = 102/103

B = 102/3x103

B = 34/103

Answer 5

\(3b=\frac{3}{1,4}+\frac{3}{1,7}+\frac{3}{7,10}+...+\frac{3}{100,103}\)\(3b=4-\frac{1}{1,4}+7-\frac{4}{4,7}+10-\frac{7}{7,10}+...+103-\frac{100}{100,103}\)\(3b=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{100}-\frac{1}{103}=1-\frac{1}{103}=\frac{102}{103}\)

\(3b=\frac{102}{3,103}=\frac{34}{103}.\)

Vay 3b se = 34/103

Answer 6

B=1/1.4+1/4.7+1/7.10+.......+1/100.103

=> ta có A=1/1-1/4+1/4-1/7+1/7-1/10+.......+1/100-1/103

3A=3/3-3/12+3/12-3/21+......+3/300-3/309

3A=3/3-3/309

A=(3/3:3)-(3/309:3)

A=1/3-1/309

A=103/309-1/309

A=34/103

đúng đấy :) chắc lun