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-27/5 . -4/15 + -4/15 . ( 2021 - 27/5)
=-4/15.[(-27/5)+2021-27/5]
=-4/15.2012,2
= -40244/75
-27/5 . -4/15 + -4/15 . ( 2021 - 27/5)
=-4/15.[(-27/5)+2021-27/5]
=-4/15.2012,2
= -40244/75
Bài 1:
Ta có: \(x-35\%\cdot x=\dfrac{1}{25}\)
\(\Leftrightarrow65\%\cdot x=\dfrac{1}{25}\)
\(\Leftrightarrow x=\dfrac{1}{25}:\dfrac{13}{20}=\dfrac{1}{25}\cdot\dfrac{20}{13}=\dfrac{4}{65}\)
Vậy: \(x=\dfrac{4}{65}\)
Bài 2:
a) Ta có: \(17\dfrac{2}{31}-\left(\dfrac{15}{17}+6\dfrac{2}{31}\right)\)
\(=17\dfrac{2}{31}-\dfrac{15}{17}-6\dfrac{2}{31}\)
\(=11+\dfrac{2}{31}-\dfrac{15}{17}\)
\(=\dfrac{5366}{527}\)
\(\frac{-27}{5}.\frac{-4}{15}+\frac{-4}{15}.\left(2010+\frac{27}{5}\right)\)
\(=\frac{-4}{15}.\left(\frac{-27}{5}+2010+\frac{27}{5}\right)\)
\(=\frac{-4}{15}.2010\)
\(=-536\)
Học tốt
\(-\frac{27}{5}.\left(-\frac{4}{15}\right)+\left(-\frac{4}{15}\right).\left(2010-\frac{-27}{5}\right)\)
\(=\left(-\frac{4}{15}\right)\left(2010-\frac{-27}{5}+\frac{-27}{5}\right)\)
\(=-\frac{4}{15}.\left(2010+\frac{27}{15}-\frac{27}{15}\right)\)
\(=-\frac{4}{15}.2010=-536\)
a)= 2021.2021-2020.(2021+1)
= 2021.(2020+1)-2020.(2021+1)
= (2021.2020)+2021-(2020.2021)-2020
= 1
b) B= (1+2-3-4)+(5+6-7-8)+(9+10-11-12)...........+(2017+2018-2019-2020)+2021
B= -4+(-4)+....................(-4)+2021
B= -4x505+2021
B= -2020 + 2021
B = 1