\(\dfrac{2}{9}+\dfrac{3}{9}=\dfrac{5}{9}\)
\(\dfrac{3}{15}+\dfrac{5}{5}=\dfrac{1}{5}+\dfrac{5}{5}=\dfrac{6}{5}\)
\(\dfrac{4}{25}+\dfrac{3}{100}=\dfrac{16}{100}+\dfrac{3}{100}=\dfrac{19}{100}\)
\(\dfrac{4}{9}+\dfrac{3}{2}=\dfrac{8}{18}+\dfrac{27}{18}=\dfrac{35}{18}\)

`2/9 +3/9=(2+3)/9=5/9`

`3/15 + 5/5 = 3/15 + 15/15 = 18/15`

`4/25 + 3/100= 16/100 + 3/100= 19/100`

`4/9 + 3/2= 8/18+ 27/18= 35/18`

\(=\) \(9^{100}+3^{200}\)

\(=\left(3^2\right)^{100}+3^{200}\)

 \(=3^{200}+3^{200}\)

\(=2.3^{200}\)

\(=9^{100}+3^{200}\)

\(=\left(3^2\right)^{100}+3^{200}\)

\(=3^{200}+3^{200}\)

\(=\left(2\times3\right)^{100}\)

\(=6^{100}\)

c/
C = 1/100-1/100-1/99-1/99-1/98-1/98-1/97-..........-1/3-1/2-1/2-1/1
C = 1/100-1/100-1/1
C = 0-1/1
C = -1

me too

Ta có \(63,1.2-21,3.6=0,9.7.10.1,2-21.3,6\)

\(=6,3.1,2-21.3,6\)

\(=0,9.7.4.3-7.3.0,9.4\)

\(=6,3.1,2-6,3.1,2\)

\(=0\)

\(\Rightarrow\dfrac{\left(1+2+......+100\right).\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{7}-\dfrac{1}{9}\right)\left(63.1,2-21.3,6\right)}{1-2+3-4+.....+99-100}=\dfrac{\left(1+2+.....+100\right)\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{7}-\dfrac{1}{9}\right)0}{1-2+3-4+......+99-100}=0\)

C=\(\frac{1}{100}-\frac{1}{100.99}-\frac{1}{99.98}-\frac{1}{98.97}-...-\frac{1}{3.2}-\frac{1}{2.1}\)

  =\(\frac{1}{100}-\left(\frac{1}{2.1}+\frac{1}{2.3}+...+\frac{1}{97.98}+\frac{1}{98.99}+\frac{1}{99.100}\right)\)

  =\(\frac{1}{100}-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{97}-\frac{1}{98}+\frac{1}{98}-\frac{1}{99}+\frac{1}{99}-\frac{1}{100}\right)\)

  =\(\frac{1}{100}-\left(1-\frac{1}{100}\right)\)

  =\(\frac{1}{100}-\frac{99}{100}\)

  =\(\frac{-98}{100}=\frac{-49}{50}\)

C=1/100 -1/100.99 -1/99.98 -1/98.97-......- 1/3.2 -1/2.1 
= 1/100 - (1/100.99 + 1/99.98 + 1/98.97-......+ 1/3.2 +1/2.1) 
Đặt A = 1/100.99 + 1/99.98 + 1/98.97-......+ 1/3.2 +1/2.1 => C = 1/100 - A 
Dễ thấy 1/2.1 = 1/1 - 1/2 
1/3.2 = 1/2 - 1/3 
..................... 
1/99.98 = 1/98 - 1/99 
1/100.99 = 1/99 - 1/100 
=> cộng từng vế với vế ta

a,=(1/3+3/5+1/15)+(3/4+-1/36)+(1/72-2/9)=1+26/36-15/72=1+(52-15)/72=1+37/72=109/72

b,=1/100-(1/1x2+1/2x3+...+1/97x98+1/98x99+1/99x100)

   =1/100-(1/1-1/2+1/2-1/3+...+1/97-1/98+1/98-1/99+1/99-1/100)

   =1/100-(1/1-1/100)=1/100-99/100=-98/100=-49/50

chỉ có mk mk giải thôi đó l-i-k-e đi

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