19 tháng 2 2022 lúc 19:45
\(\dfrac{1}{2}.\dfrac{3}{5}+\dfrac{4}{7}:\dfrac{4}{5}-\dfrac{1}{70}\)
\(=\dfrac{3}{10}+\dfrac{4}{7}.\dfrac{5}{4}-\dfrac{1}{70}\)
\(=\dfrac{3}{10}+\dfrac{20}{28}-\dfrac{1}{70}\)
\(=\dfrac{3.14}{10.14}+\dfrac{20.5}{28.5}-\dfrac{1.2}{70.2}\)
\(=\dfrac{42}{140}+\dfrac{100}{140}-\dfrac{2}{140}\)
\(=\dfrac{42+100-2}{140}\)
\(=\dfrac{140}{140}\)
\(=1\)
Học tốt nhé.
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