ta có: \(1-\frac{5}{6}+\frac{7}{12}-\frac{9}{20}+\frac{11}{30}-\frac{13}{42}+\frac{15}{56}-\frac{17}{72}+\frac{19}{90}\)
\(=1-\frac{5}{2.3}+\frac{7}{3.4}-\frac{9}{4.5}+\frac{11}{5.6}-\frac{13}{6.7}+\frac{15}{7.8}-\frac{17}{8.9}+\frac{19}{9.10}\)
\(=1-\frac{1}{2}-\frac{1}{3}+\frac{1}{4}-\frac{1}{4}+\frac{1}{5}-\frac{1}{5}+\frac{1}{6}-\frac{1}{6}+\frac{1}{7}-\frac{1}{7}+\frac{1}{8}-\frac{1}{8}+\frac{1}{9}-\frac{1}{9}+\frac{1}{10}\)
\(=1-\frac{1}{2}+\frac{1}{10}=\frac{3}{5}\)
\(1-\frac{5}{2.3}+\frac{7}{3.4}-\frac{9}{4.5}+\frac{11}{5.6}-\frac{13}{6.7}+\frac{15}{7.8}-\frac{17}{8.9}+\frac{19}{9.10}\)
tùy you giải z, t bt tek thui -_-
1 - \(\frac{5}{2.3}+\frac{7}{3.4}-\frac{9}{4.5}+\frac{11}{5.6}-\frac{13}{6.7}+\frac{15}{7.8}-\frac{17}{8.9}+\frac{19}{9.10}\)
giải dc chưa
dc rồi thì k cho mình nha
Xem mình làm thế này có đúng ko
=\(1-\left(\frac{5}{2}-\frac{5}{3}\right)+\left(\frac{7}{3}-\frac{7}{4}\right)-\left(\frac{9}{4}-\frac{9}{5}\right)+\left(\frac{11}{5}-\frac{11}{6}\right)-\left(\frac{13}{6}-\frac{13}{7}\right)+\frac{15}{7}-\frac{15}{8}\)
\(-\left(\frac{17}{8}-\frac{17}{9}\right)+\frac{19}{9}-\frac{19}{10}\)
=1- 5/2 +5/3 + 7/3 -7/4- 9/4+ 9/5 +11/5 - 11/6- 13/6+13/7 + 15/7 - 15/8 -17/8 + 17/9+19/9-19/10
=1+(5/3+7/3-7/4-9/4)+(9/5+11/5-11/6-13/6)+(13/7+15/7-15/8-17/8)+(17/9+19/9-19/10-5/2)
=1+0+0+0+4-44/10
=5-44/10=3/5
Nguyễn Tuấn Minh: you lm đúng òi đó