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=\(\dfrac{1}{18}-\dfrac{1}{23}+\dfrac{1}{23}-\dfrac{1}{24}+\dfrac{1}{24}-\dfrac{1}{31}+\dfrac{1}{31}-\dfrac{1}{33}+\dfrac{1}{33}-\dfrac{1}{37}+\dfrac{1}{37}-\dfrac{1}{38}\)
=\(\dfrac{1}{18}-\dfrac{1}{38}=\dfrac{19-9}{38x9}=\dfrac{10}{342}=\dfrac{5}{171}\)
\(\dfrac{5}{18\times23}+\dfrac{1}{23\times24}+\dfrac{7}{24\times31}+\dfrac{2}{31\times33}+\dfrac{4}{33\times37}+\dfrac{1}{37\tímes38}\)
\(\dfrac{23-18}{18\times23}+\dfrac{24-23}{23\times24}+\dfrac{31-24}{24\times31}+\dfrac{33-31}{31\times33}+\dfrac{37-33}{33\times37}+\dfrac{38-37}{37\times38}\)
\(\dfrac{23}{18\times23}-\dfrac{18}{18\times23}+\dfrac{24}{23\times24}-\dfrac{23}{23\times24}+\dfrac{31}{24\times31}-\dfrac{24}{24\times31}+\dfrac{33}{31\times33}-\dfrac{31}{31\times33}+\dfrac{37}{33\times37}-\dfrac{33}{33\times37}+\dfrac{38}{37\times38}-\dfrac{37}{37\times38}\)
\(\dfrac{1}{18}-\dfrac{1}{23}+\dfrac{1}{23}-\dfrac{1}{24}+\dfrac{1}{24}-\dfrac{1}{31}+\dfrac{1}{31}-\dfrac{1}{33}+\dfrac{1}{33}-\dfrac{1}{37}+\dfrac{1}{37}-\dfrac{1}{38}\)
\(\dfrac{1}{18}-\dfrac{38}=\dfrac{5}{171}\)
Sửa đề:
\(\frac{1}{33}\times\left(\frac{33}{12}+\frac{3333}{2020}+\frac{333333}{303030}+\frac{33333333}{42424242}\right)\)
\(=\frac{1}{33}\times\frac{33}{12}+\frac{1}{33}\times\frac{3333}{2020}+\frac{1}{33}\times\frac{333333}{303030}+\frac{1}{33}\times\frac{33333333}{42424242}\)
\(=\frac{1}{12}+\frac{33\times101}{33\times101\times20}+\frac{33\times10101}{33\times10101\times30}+\frac{33\times1010101}{33\times1010101\times42}\)
\(=\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\)
\(=\frac{1}{3x4}+\frac{1}{4x5}+\frac{1}{5x6}+\frac{1}{6x7}\)
\(=\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\)
\(=\frac{1}{3}-\frac{1}{7}\)
\(=\frac{4}{21}\)
TÌM X
x-2 1/5=33/20
2 1/5 là hỗn số, 2 là phần nguyên 1/5 là phần phân số. 33/20 cũng là một phân số.
\(x-2\frac{1}{5}=\frac{33}{20}\)
\(x-\frac{11}{5}=\frac{33}{20}\)
\(x=\frac{33}{20}-\frac{11}{5}\)
\(x=-\frac{11}{20}\)
1/31 + 1/32 + 1/33 + ... + 1/90
= (1/31 + 1/32 + ... + 1/60) + (1/61 + 1/62 + ... + 1/90)
> 1/60 × 30 + 1/90 × 30
> 1/2 + 1/3
> 5/6
1+1=2 nha
1+1= 3
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