a = 36

b=149/63

thanks

Ta có \(70\left(\frac{121212}{565656}+\frac{121212}{727272}+\frac{121212}{909090}\right)\)

\(=70\left(\frac{3\cdot40404}{14\cdot40404}+\frac{121212}{121212\cdot6}+\frac{2\cdot60606}{15\cdot60606}\right)\)

\(=70\left(\frac{3}{14}+\frac{1}{6}+\frac{2}{15}\right)\)

\(=70\cdot\frac{18}{35}=36\)

Đặt 

\(A=210.\left(\frac{111111}{121212}+\frac{111111}{202020}+\frac{111111}{303030}+\frac{111111}{424242}+\frac{111111}{565656}+\frac{111111}{727272}+\frac{111111}{909090}\right)\)

     \(=210.\left(\frac{11}{12}+\frac{11}{20}+\frac{11}{30}+\frac{11}{42}+\frac{11}{56}+\frac{11}{72}+\frac{11}{90}\right)\)

    \(=210.11\left(\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}\right)\)

     \(=2310.\left(\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}\right)\)

    \(=2310.\left(\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\right)\)

     \(=2310.\left(\frac{1}{3}-\frac{1}{10}\right)\)

       \(=2310.\frac{7}{30}\)

        \(=539\)

210.(111111/121212 +111111/202020+11111/303030 + 111111/424242 +111111/565656 +111111/727272 +111111/909090)

= 210 . ( 11/12+11/20+11/42+11/56+11/72+11/90)

= 210.(11.(1/12+1/20+1/42+1/56+1/72+1/90))

=210.(11(1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10))

=210.(11.(1/3-1/10))

=210.(11.7/30)

=210.77/30

=593

 T I C K    GIÙM MIK

\(\frac{121212}{151515}+\frac{121212}{353535}+\frac{121212}{636363}+\frac{121212}{999999}\)

= \(\frac{12.10101}{15.10101}+\frac{12.10101}{35.10101}+\frac{12.10101}{63.10101}+\frac{12.10101}{99.10101}\)

= \(\frac{12}{15}+\frac{12}{35}+\frac{12}{63}+\frac{12}{99}\)

= \(\frac{12}{3.5}+\frac{12}{5.7}+\frac{12}{7.9}+\frac{12}{9.11}\)

= \(6.\left(\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}\right)\)

= \(6.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}\right)\)

= \(6.\left(\frac{1}{3}-\frac{1}{11}\right)\)

= \(6.\frac{8}{33}\)

= \(\frac{16}{11}\)

70.(13/56+13/72+13/90)

=70.39/70=39

đúg nha

B=39 tick cho mình nha nha nha nha

\(B=70\cdot\left(\frac{131313}{565656}+\frac{131313}{727272}+\frac{131313}{909090}\right)\)

\(B=70\cdot\left(\frac{13}{56}+\frac{13}{72}+\frac{13}{90}\right)\)

\(B=70\cdot\frac{39}{70}\)

\(B=39\)

Vậy B = 39

B=\(70\times\left(\frac{131313}{565656}+\frac{131313}{727272}+\frac{131313}{909090}\right)\)

B=\(70\times\left(\frac{13}{56}+\frac{13}{72}+\frac{13}{90}\right)\)

B=\(70\times\frac{39}{70}\)

B=\(39\)

Nếu mk làm sai thì xin lỗi bạn nhiều nha

B=70.(13.1010156.10101+13.1010172.10101+13.1010190.10101)(56.1010113.10101​+72.1010113.10101​+90.1010113.10101​)

B=70.(1356+1372+1390)(5613​+7213​+9013​)

B=70.39707039​=39

nhớ tick cho mình nhe