Question

[đỗ phương anh]

B=1.4+4.7+......+100+103

Answer 1

[Sherlockichi Kazukosho]

\(B=1.4+4.7+....+100.103\)

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

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

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

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

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

Answer 2

[đỗ phương anh]

thực ra dấu chấm là dấu nhân