Dễ thôi bạn!
1/3.4+1/4.5+1/5.6+...+1/99.100
=1/3-1/4+1/4-1/5+1/5-1/6+...+1/98-1/99+1/99-1/100
=1/3-1/100
=97/300
\(\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+...+\frac{1}{99.100}\)
\(=\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{99}-\frac{1}{100}\)
\(=\frac{1}{3}-\frac{1}{100}\)
\(=\frac{97}{300}\)
1/3.4 + 1/ 4.5 + 1/5.6 + ... + 1/99.100
= 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 + ... + 1/99 - 1/100
= 1/3 -1/100
= 97/300
Ta có: \(\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+..+\frac{1}{99}-\frac{1}{100}\)\(=\frac{1}{3}-\frac{1}{100}=\frac{97}{300}\)
\(\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+...+\frac{1}{99.100}\)
\(=\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{99}-\frac{1}{100}\)
\(=\frac{1}{3}-\frac{1}{100}=\frac{100}{300}-\frac{3}{300}=\frac{97}{300}\)
