c) 1 $\frac{1}{21}$ : ( 15,75 - 15 $\frac{1}{4}$ ) + 2 $\frac{1}{12}$ : ( 7 $\frac{3}{4}$ - 7,25 )

    = ( 1 + $\frac{1}{21}$ ) : ( 15,75 - ( 15 + $\frac{1}{4}$ ) ) + ( 2 + $\frac{1}{12}$ ) : ( ( 7 + $\frac{3}{4}$ ) - 7,25 )

    = ( 1 + $\frac{1}{21}$ ) : ( 15,75 - 15 - $\frac{1}{4}$  ) + ( 2 + $\frac{1}{12}$ ) : ( 7 + $\frac{3}{4}$ - 7,25  )

    = ( 1 + $\frac{1}{21}$ ) : 0,5 + ( 2 + $\frac{1}{12}$ ) : 0,5

    = ( 1 + $\frac{1}{21}$ ) x 2 + ( 2 + $\frac{1}{12}$ ) x 2

    = ( $\frac{22}{21}$ + $\frac{25}{12}$ ) x 2

    = $\frac{263}{42}$

d) Ta có: ( $\frac{1}{3}$ + $\frac{1}{4}$ - $\frac{7}{12}$ ) = 0

  Nên: ( $\frac{2017}{2021}$ + $\frac{2018}{2019}$ + $\frac{2020}{2023}$ ) x ( $\frac{1}{3}$ + $\frac{1}{4}$ - $\frac{7}{12}$ ) = 0

e) $\frac{2019 x 2021 + 2020}{2020 x 2021 - 1}$

   = $\frac{2019 x 2021 + 2020}{ (2019 + 1 ) x 2021 - 1}$

   = $\frac{2019 x 2021 + 2020}{ 2021 x 2019 + 2021 x 1 - 1}$

   = $\frac{2019 x 2021 + 2020}{ 2021 x 2019 + 2020}$

   = 1

f) $\frac{637 x 527 - 189}{526 x 637 + 448}$

   = $\frac{637 x ( 526 + 1 ) - 189}{526 x 637 + 448}$

   = $\frac{637 x 526 + 637 x 1 - 189}{526 x 637 + 448}$

   = $\frac{637 x 526 + 448}{526 x 637 + 448}$

   = 1

 ~ xin câu trả lời hay nhất nhé! ~

Đáp án:

 c,1.1/21:(15,75-15.1/4)+2.1/12:(7.3/4-7,25)

=1/21:(63/4-61/4)+25/12:(31/4-29/4)

=1/21:1/2+25/12:1/2

=1/21×2+25/12×2

=2×(1/21+25/12)

=2×179/84

=179/42

d,(2017/2021+2018/2019+2020/2023)×(1/3+1/4-7/12)

=(2017/2021+2018/2019+2020/2023)×0

=0

e,2019×2021+2020

   2020×2021-1

 =2019×2020

     2020×1

  =2019

       1

   =2019

f,637×527-189

  526×637+448

=527-198

   526+448

=329

   974

cho tui câu trả lời hay nhất nha

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