Tìm tập hợp các số nguyên \(x\), biết:
a) \(4\dfrac{5}{9}:2\dfrac{5}{8}-7< x< \left(3\dfrac{1}{5}:3,2+4,5.1\dfrac{31}{45}\right):\left(-21\dfrac{1}{2}\right)\)
b) \(\dfrac{-17}{21}:\left(\dfrac{5}{4}-\dfrac{2}{5}\right)< x+\dfrac{4}{7}< 1-\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}\)
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a )
\(4\dfrac{5}{9}:2\dfrac{5}{8}-7=-\dfrac{995}{189}=-5\) ( đã làm tròn )
\(\left(3\dfrac{1}{5}:3,2+4,5.1\dfrac{31}{45}\right):\left(-21\dfrac{1}{2}\right)\) \(=\dfrac{2}{5}=0\) ( đã làm tròn )
Ta có :
\(-5< x< 0\)
\(\Rightarrow x=\left\{-4;-3;-2;-1\right\}\)
b )
\(-\dfrac{17}{21}:\left(\dfrac{5}{4}-\dfrac{2}{5}\right)=-\dfrac{20}{21}=-1\) ( đã làm tròn )
\(1-\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}=\dfrac{7}{12}=1\) ( đã làm tròn )
Ta có : \(-1< x+0,6< 1\)
\(\Rightarrow x=\left\{-1;0\right\}\)
a) \(4\dfrac{5}{9}:2\dfrac{5}{8}-7< x< \left(3\dfrac{1}{5}:3,2+4,5\cdot1\dfrac{31}{45}\right):\left(-21\dfrac{1}{2}\right)\)
\(\Leftrightarrow\left\{{}\begin{matrix}x>4\dfrac{5}{9}:2\dfrac{5}{8}-7\\x< \left(3\dfrac{1}{5}:3,2+4,5\cdot1\dfrac{31}{45}\right):\left(-21\dfrac{1}{2}\right)\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x>-\dfrac{227}{36}\\x< -\dfrac{2}{5}\end{matrix}\right.\)
\(\Leftrightarrow-\dfrac{2}{5}>x>-\dfrac{227}{36}\)
b) \(-\dfrac{17}{21}:\left(\dfrac{5}{4}-\dfrac{2}{5}\right)< x+\dfrac{4}{7}< 1-\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}\)
\(\Leftrightarrow\left\{{}\begin{matrix}x+\dfrac{4}{7}>-\dfrac{17}{21}:\left(\dfrac{5}{4}-\dfrac{2}{5}\right)\\x+\dfrac{4}{7}< 1-\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x>-\dfrac{32}{21}\\x< \dfrac{1}{84}\end{matrix}\right.\)
\(\Leftrightarrow\dfrac{1}{84}>x>-\dfrac{32}{21}\)
