Question

[Nguyễn Hà Phương]

\(A=\frac{7}{6}+\frac{13}{12}+\frac{21}{20}+\frac{31}{30}+...+\frac{9901}{9900}\)

\(B=\frac{2}{3}+\frac{5}{6}+\frac{9}{10}+\frac{14}{15}+...+\frac{4949}{4950}\)

Answer 1

[✓ ℍɠŞ_ŦƦùM $₦G ✓]

\(A=\frac{7}{6}+\frac{13}{12}+\frac{21}{20}+...+\frac{9901}{9900}=\left(1+\frac{1}{2.3}\right)+\left(1+\frac{1}{3.4}\right)+\left(1+\frac{1}{4.5}\right)+...+\left(1+\frac{1}{99.100}\right)\)\(=\left(1+1+1+...+1\right)+\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{99.100}\right)\)

\(=98+\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{99}-\frac{1}{100}\right)=98+\left(\frac{1}{2}-\frac{1}{100}\right)\)

\(=98+\frac{49}{100}=98\frac{49}{100}\)