1.Thực hiện phép tính: a) 3/8 – 5/6 + 1/4 b) 1/7 : ( 2 – 1 và 5/7 ) + 3/2 giúp mk vs

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1. $\text { Đáp án: }$

   $\text { a) }$ $\frac {3}{8}$ $–$ $\frac {5}{6}$ $+$ $\frac {1}{4}$

   $=$ $\frac {9}{24}$ $–$ $\frac {20}{6}$ $+$ $\frac {6}{24}$

   $=$ $\frac {–5}{24}$

   $\text { b) }$ $\frac {1}{7}$ $\text { : ( 2 – 1 }$ $\frac {5}{7}$ $\text { ) + }$ $\frac {3}{2}$

   $=$ $\frac {1}{7}$ $\text { : ( 2 – }$ $\frac {12}{7}$ $\text { ) + }$ $\frac {3}{2}$

   $=$ $\frac {1}{7}$ $:$ $\frac {2}{7}$ $+$ $\frac {3}{2}$

   $=$ $\frac {1}{7}$ $.$ $\frac {7}{2}$ $+$ $\frac {3}{2}$

   $=$ $\frac {1}{2}$ $+$ $\frac {3}{2}$

   $=$ $\frac {3}{3}$ $=$ $1$

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2. a) $\dfrac{3}{8}-\dfrac{5}{6}+\dfrac{1}{4}$

   $=\dfrac{9}{24}-\dfrac{20}{24}+\dfrac{6}{24}$

   $=\dfrac{9-20+6}{24}$

   $=\dfrac{-5}{24}$

   b) $\dfrac{1}{7}:(2-1\dfrac{5}{7})+\dfrac{3}{2}$

   $=\dfrac{1}{7}:(2-\dfrac{12}{7})+\dfrac{3}{2}$

   $=\dfrac{1}{7}:\dfrac{2}{7}+\dfrac{3}{2}$

   $=\dfrac{1}{2}+\dfrac{3}{2}$

   $=\dfrac{4}{2}$

   $=2$

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