Question

Tính A

A = 1/1.5 + 1/5.8 + 1/8.11 + ... + 1/98.101

Answer 1

1/2.5 nhé

Answer 2

\(A=\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+...+\frac{1}{98.101}\)

\(3A=\frac{3}{2.5}+\frac{3}{5.8}+\frac{3}{8.11}+...+\frac{3}{98.101}\)

\(3A=\frac{5-2}{2.5}+\frac{8-5}{5.8}+\frac{11-8}{8.11}+...+\frac{101-98}{98.101}\)

\(3A=\frac{5}{2.5}-\frac{2}{2.5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+...+\frac{1}{98}-\frac{1}{101}\)

\(3A=\frac{1}{2}-\frac{1}{101}=\frac{99}{202}\)

\(\Leftrightarrow A=\frac{99}{202}\div3\)

\(\Rightarrow A=\frac{33}{202}\)

Answer 3

33/202 nha bn