a) \(15\times\left(\frac{212121}{434343}+\frac{333333}{353535}\right)=15\times\left(\frac{21\times10101}{43\times10101}+\frac{33\times10101}{35\times10101}\right)\)

\(=15\times\left(\frac{21}{43}+\frac{33}{35}\right)=\frac{6462}{301}\)

b) \(\frac{639\times721721}{721\times639639}=\frac{639\times721\times1001}{721\times639\times1001}=1\)

c) \(\frac{327\times412+400}{328\times412-12}=\frac{\left(328-1\right)\times412+400}{328\times412-12}=\frac{328\times412-412+400}{328\times412-12}\)

\(=\frac{328\times412-12}{328\times412-12}=1\)

d) \(9\times\left(\frac{151515}{171717}+\frac{131313}{181818}\right)=9\times\left(\frac{15\times10101}{17\times10101}+\frac{13\times10101}{18\times10101}\right)=9\times\left(\frac{15}{17}+\frac{13}{18}\right)\)

\(=9\times\frac{491}{306}=\frac{491}{34}\)

thank bn

\(a)15.\left(\dfrac{212121}{434343}+\dfrac{333333}{353535}\right)\)

\(=15.\left(\dfrac{21}{43}+\dfrac{33}{35}\right)\)

\(=15.\dfrac{2154}{1505}\)

\(=\dfrac{6462}{301}\)

\(=15.\left(\frac{21.10101}{43.10101}-\frac{33.10101}{35.10101}\right)\)

\(=15.\left(\frac{21}{43}-\frac{33}{35}\right)\)

\(=15.\frac{-684}{1505}=\frac{-2052}{301}\)

ki hieu . la nhan do nha ban len cap 2 se thay dau x = .

làm sai hết rồi phan văn hiếu à

\(=\frac{327.412+400}{327.412+412-12}=\frac{327.412+400}{327.412+400}=1\)

a)=15.(21/43+33?55)=15.234/215=16 14/43
b)=328.412-412+400/328.412-12=328.412-12/328.412-12=1
c)7217721 hay là 721721 vậy?
 

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

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

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

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

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

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

MK KO BIẾT TÌNH NHANH ĐÂU! MK CHỈ LÀM ĐC NHƯ VẬY THÔI!!!!
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

\(\frac{3}{2}.x-70\frac{10}{11}:\left(\frac{131313}{151515}+\frac{131313}{353535}+\frac{131313}{636363}+\frac{131313}{999999}=-5\right)\)

\(\frac{3}{2}.x-70\frac{10}{11}:\left(\frac{13}{15}+\frac{13}{35}+\frac{13}{63}+\frac{13}{99}\right)=-5\)

\(\frac{3}{2}.x-70\frac{10}{11}:\left[13\times\left(\frac{1}{15}+\frac{1}{35}+\frac{1}{63}+\frac{1}{99}\right)\right]=-5\)

\(\frac{3}{2}.x-70\frac{10}{11}:\left[13\times\left(\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}+\frac{1}{9.11}\right)\right]=-5\)

\(\frac{3}{2}.x-70\frac{10}{11}:\left[13\times\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}\right)\right]=-5\)

\(\frac{3}{2}.x-70\frac{10}{11}:\left[13\times\left(\frac{1}{3}-\frac{1}{11}\right)\right]=-5\)

\(\frac{3}{2}.x-\frac{45}{2}=-5\)

\(\frac{3}{2}.x=\frac{35}{2}\)

\(x=\frac{35}{3}\)

bài phát sai òi hihi cần mk chỉ chỗ sai ko

x= 80/3 đúng ko các bạn