A) \(\frac{131313}{151515}+\frac{131313}{353535}+\frac{131313}{636363}+\frac{131313}{999999}\)

\(=\frac{10101\times13}{10101\times15}+\frac{10101\times13}{10101\times35}+\frac{10101\times13}{10101\times63}+\frac{10101\times13}{10101\times99}\)

\(=\frac{13}{15}+\frac{13}{35}+\frac{13}{63}+\frac{13}{99}\)

\(=13\times\left(\frac{1}{15}+\frac{1}{35}+\frac{1}{63}+\frac{1}{99}\right)\)

\(=13\times\frac{4}{33}=\frac{52}{33}\)

B) \(\left(1998:18-1443:13\right)\times\left(16996-1110:30\times305\right)\)

\(=\left(111-111\right)\times\left(16996-1110:30\times305\right)\)

\(=0\times\left(16996-1110:30\times305\right)\)

\(=0\)

( TẤT CẢ MỌI SỐ NHÂN VỚI 0 ĐỀU BẰNG 0)

C) \(\left(\frac{575757}{424242}+\frac{575757}{565656}+\frac{575757}{727272}\right)\times18\)

\(=\left(\frac{10101\times57}{10101\times42}+\frac{10101\times57}{10101\times56}+\frac{10101\times57}{10101\times72}\right)\times8\)

\(=\left(\frac{57}{42}+\frac{57}{56}+\frac{57}{72}\right)\times8\)

\(=\left(\frac{1}{42}+\frac{1}{56}+\frac{1}{72}\right)\times57\times8\)

\(=\frac{1}{169344}\times57\times8\)

\(=\frac{19}{7056}\)

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CHÚC BN HỌC TỐT!!!!!!

 a, = 13/15 + 13/35 + 13/63 + 13/99

    = 13.( 1/15 + 1/35 + 1/63 + 1/99 )

   = 13.( 1/ 3.5 + 1/5.7 + 1/7.9 + 1/ 9.11)

 = 13 . ( 1/3 - 1/5 +1/5 - 1/7 + 1/7 - 1/9 + 1/9 - 1/11)

 = 13 . ( 1/3 - 1/11)

= 13 . 3/11 = 39/11

\(=\left(\frac{57}{42}+\frac{57}{56}+\frac{57}{72}\right)\times18\)

\(=\frac{19}{6}\times18=57\)

= (57/42 +57/56 + 57/72),18

=(1/6.7 +1/7.8 +1/8.9).18.57

=(1/6-1/7 +1/7 -1/8 +1/8-1/9).18.57

=(1/6-1/9) .18 .57

=57.3 - 57.2

=57

57 bạn nhé

\(\frac{575757}{424242}+\frac{575757}{565656}+\frac{575757}{727272}=\frac{57\times10101}{42\times10101}+\frac{57\times10101}{56\times10101}+\frac{57\times10101}{72\times10101}\)

\(=\frac{57}{42}+\frac{57}{56}+\frac{57}{72}=57\times\left(\frac{1}{42}+\frac{1}{56}+\frac{1}{72}\right)\)

\(=57\times\left(\frac{1}{6\times7}+\frac{1}{7\times8}+\frac{1}{8\times9}\right)\)

\(=57\times\left(\frac{7-6}{6\times7}+\frac{8-7}{7\times8}+\frac{9-8}{8\times9}\right)\)

\(=57\times\left(\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}\right)\)

\(=57\times\left(\frac{1}{6}-\frac{1}{9}\right)=\frac{19}{6}\)

rut gon

= (57/42+57/56+57/72)*18

=19/6*18

=57

ta có:

575757/424242 = 57/42

575757/565656 = 57/56

575757/727272 = 57/72

suy ra:

(57/42 +57/56 +57/72)x 18 = 57

=57

Ai k mk mk se k lai

57 nha ban Ngoc Anh

\(\left(\frac{575757}{424242}+\frac{575757}{565656}+\frac{575757}{727272}\right)\cdot18\)

\(=\left(\frac{19}{14}+\frac{57}{56}+\frac{19}{24}\right)\cdot18\)

\(=\left(\frac{228+171+133}{168}\right)\cdot18\)

\(=\frac{532}{168}\cdot18\)

\(=\frac{19}{6}\cdot8\)

\(=\frac{76}{3}\)

 = 57 (chắc chắn đúng)

\(\left(\frac{575757}{424242}+\frac{575757}{565656}+\frac{575757}{727272}\right)\cdot18=\left(\frac{57}{42}+\frac{57}{56}+\frac{57}{72}\right)\cdot18=\frac{57}{42}\cdot18+\frac{57}{56}\cdot18+\frac{57}{72}\cdot18=\frac{171}{7}+\frac{513}{28}+\frac{57}{4}=\frac{684}{28}+\frac{513}{28}+\frac{399}{28}=\frac{1596}{28}=57\)

(575757/424242 + 575757/565656 + 575757/727272) x 18
= (57/42 + 57/56 + 57/72) x 18 
= 57x3/7 + 57x9/28 + 57/4
= 1596/28
= 57