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! ~
