$\frac{13}{20}$ + $\frac{13}{30}$ + $\frac{13}{42}$ + $\frac{13}{56}$ + $\frac{13}{72}$ + $\frac{13}{90}$
= $\frac{13}{4.5}$ + $\frac{13}{5.6}$ + $\frac{13}{6.7}$ +$\frac{13}{7.8}$ +$\frac{13}{8.9}$ + $\frac{13}{9.10}$
=$\frac{13}{4}$ - $\frac{13}{5}$ + $\frac{13}{5}$ -$\frac{13}{6}$ +$\frac{13}{6}$ -$\frac{13}{7}$ + $\frac{13}{7}$ - $\frac{13}{8}$ + $\frac{13}{8}$ - $\frac{13}{9}$ +$\frac{13}{9}$ - $\frac{13}{10}$
= $\frac{13}{4}$ - $\frac{13}{10}$
= $\frac{65}{20}$ - $\frac{26}{20}$
=$\frac{39}{20}$
Cho mik 5 sao và câu trả lời hay nhất nha bạn
