2323/202+2323/606+2323/1212+2323/2020+2323/3030+2323/4242+2323/5656+2323/7272+2323/9090.=

\(\frac{23\times101}{2\times101}+\frac{23\times101}{6\times101}+\frac{23\times101}{12\times101}+....+\frac{23\times101}{72\times101}+\frac{23\times101}{90\times101} \)

=\(\frac{23}{2}+\frac{23}{6}+..........+\frac{23}{72}+\frac{23}{90}\)

=\(23\times\left(\frac{1}{1\times2}+\frac{1}{2\times3}+.....+\frac{1}{9\times10}\right)\)

=\(23\times\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}_{ }\right)\)

=\(23\left(1-\frac{1}{10}\right)_{ }\)

=\(23\times\frac{9}{10}\)

==\(\frac{207}{10}\)           

chúc học giỏi nha bn

21116070

10843158 nha

a/

=2323 x (3434+5656)

=2323 x 9090

=21 116 070

b/

=1234 x (4244+4543)

=1234 x 8787

=10 843 159

\(\dfrac{121212}{353535}+-\dfrac{2323}{4242}\)

\(=\dfrac{12}{35}+-\dfrac{23}{42}\)

\(=-\dfrac{43}{210}\)

\(=\dfrac{12}{35}-\dfrac{23}{42}=\dfrac{72-115}{210}=\dfrac{-43}{210}\)

19/37

\(\dfrac{2323}{1818}\) .  \(\dfrac{7272}{6969}\) 

= \(\dfrac{23\cdot101}{18\cdot101}\) . \(\dfrac{18\cdot4\cdot101}{23\cdot3\cdot101}\) 

= \(\dfrac{23}{18}\cdot\dfrac{18\cdot4}{23\cdot3}=\dfrac{4}{3}\)

x=1/28

x = 2323/4646-1313/2828

x= 1/28

\(\dfrac{1313}{2828}+x=\dfrac{2323}{4646}\\ \dfrac{13}{28}+x=\dfrac{1}{2}\\ x=\dfrac{1}{2}-\dfrac{13}{28}\\ x=\dfrac{14}{28}-\dfrac{13}{28}\\ x=\dfrac{1}{28}\)