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b)
\(4\frac{5}{9}:2\frac{5}{18}-7< x< \left(3\frac{1}{5}:3,2+4,5.1\frac{31}{45}\right):\left(21.\frac{1}{2}\right)\)
\(\Rightarrow\frac{41}{9}:\frac{41}{18}-7< x< \left(\frac{16}{5}:\frac{16}{5}+\frac{9}{2}.\frac{76}{45}\right):\frac{21}{2}\)
\(\Rightarrow2-7< x< \left(1+\frac{38}{5}\right):\frac{21}{2}\)
\(\Rightarrow-5< x< \frac{43}{5}:\frac{21}{2}\)
\(\Rightarrow-5< x< \frac{86}{105}\)
Vì \(x\in Z\left(gt\right)\)
\(\Rightarrow x\in\left\{-4;-3;-2;-1;0\right\}.\)
Vậy \(x\in\left\{-4;-3;-2;-1;0\right\}.\)
\(\frac{2}{3}\) .\(\frac{3}{4}\)\(\le\)\(\frac{x}{18}\) \(\le\)\(\frac{7}{3}\).\(\frac{1}{3}\)
\(\frac{1}{2}\le\frac{x}{18}\le\frac{7}{9}\)
\(\frac{9}{18}\le\frac{x}{18}\le\frac{14}{18}\)
\(\Rightarrow x\in\){9:10;11;12;13;14}
\(\frac{2}{3}.\left(\frac{1}{2}+\frac{3}{4}-\frac{1}{3}\right)\le\frac{x}{18}\le\frac{7}{3}.\left(\frac{1}{2}-\frac{1}{6}\right)\)
\(\frac{2}{3}.\left(\frac{5}{4}-\frac{1}{3}\right)\le\frac{x}{18}\le\frac{7}{3}.\frac{1}{3}\)
\(\frac{2}{3}.\frac{11}{12}\le\frac{x}{18}\le\frac{7}{9}\)
\(\frac{11}{18}\le\frac{x}{18}\le\frac{7}{9}\)
\(\frac{11}{18}\le\frac{x}{18}\le\frac{14}{18}\)
Vậy \(x\in\left\{11;12;13\right\}\)
\(\frac{6}{7}-\frac{5}{21}+\left[3\frac{1}{3}-4\frac{1}{14}\right]=x-\left[\frac{1}{2}-\left|-\frac{1}{3}\right|\right]\)
\(\Leftrightarrow\frac{18}{21}-\frac{5}{21}+\left[\frac{10}{3}-\frac{57}{14}\right]=x-\left[\frac{1}{2}-\frac{1}{3}\right]\)
\(\Leftrightarrow\frac{13}{21}+\left[-\frac{31}{42}\right]=x-\frac{1}{6}\)
\(\Leftrightarrow-\frac{5}{42}=x-\frac{1}{6}\Leftrightarrow-\frac{5}{42}-x=-\frac{1}{6}\)
\(\Leftrightarrow x=-\frac{5}{42}-\left[-\frac{1}{6}\right]=\frac{1}{21}\)
\(\left(\frac{3}{5}.x-\frac{2}{3}.x-x\right).\frac{1}{7}=\frac{-5}{21}\)
\(\Rightarrow x.\left(\frac{3}{5}-\frac{2}{3}-1\right).\frac{1}{7}=\frac{-5}{21}\)
\(\Rightarrow x.\frac{-16}{105}=\frac{-5}{21}\)
\(\Rightarrow x=\frac{-5}{21}:\frac{-16}{105}\)
\(\Rightarrow x=\frac{25}{16}\)
x.[3/5-2/3-1]=-5/21:1/7
x.-16/15=-5/3
x=-5/3:-16/15
x=25/16
Ta có: \(-\frac{2}{3}=-0,6666666...\)
và \(-\frac{1}{7}=-0,142857...\)
=> -0,666666... < \(\frac{x}{21}\)< -0,142857...
Mà \(x\in Z\)
=> không tìm được x
khong phai lop 6