210 + 46 + – 210 + – 26 = 210 + 46 + – 210 + – 26 = 210 + – 210 + 46 + − 26 = 0 + 20 = 20.

a/ \(=\frac{21}{23}+\frac{125}{143}-\frac{101.21}{101.23}-\frac{1001.125}{1001.143}=0\)

b/ \(=\frac{4}{20}+\frac{8}{21}+\frac{2}{5}-\frac{3}{5}+\frac{2}{21}-\frac{10}{21}+\frac{3}{20}=\frac{7}{20}-\frac{1}{5}=\frac{4}{20}\)

c/ \(\frac{C}{2}=\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{420}=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{20.21}\)

\(\frac{C}{2}=\frac{3-2}{2.3}+\frac{4-3}{3.4}+\frac{5-4}{4.5}+...+\frac{21-20}{20.21}=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{20}-\frac{1}{21}\)

\(\frac{C}{2}=\frac{1}{2}-\frac{1}{21}=\frac{19}{42}\Rightarrow C=\frac{19}{21}\)

= 210 + 46 -210 -26

= (210 - 210 ) + ( 46 - 26 )

= 0 + 20

= 20 

Chúc bạn học giỏi ! Kết bạn với mình nha

\(=210+46-210-26\)

\(=\left(210-210\right)+\left(46-26\right)\)

\(=0+20\)

\(=20\)

a ) 1 2 . b ) − 2 5 . c ) − 7 8 . d ) 0. e ) 0.

Lời giải:

$A=(1-4)+(7-10)+(13-16)+....+(97-100)+103$

$=\underbrace{(-3)+(-3)+(-3)+...+(-3)}_{17}+103$

$=(-3).17+103=52$

 \(=210+46+\left(-210\right)+\left(-26\right)\)

\(=[210+\left(-210\right)]+[46+\left(-26\right)]\)

\(=0+20\) 

 =20

giúp mik với

Lời giải:
$(-8).72+8(-19)-(-8)=(-8).72+(-8).19-(-8)$

$=(-8)(72+19-1)=(-8)(72+18)=(-8).90=-720$