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Trả lời :
\(\left(\frac{1}{4}+0,75\right)\div\frac{5}{7}+\frac{2}{5}+\left|2021\right|\)
\(=\left(\frac{1}{4}+\frac{3}{4}\right)\div\frac{5}{7}+\frac{2}{5}+2021\)
\(=1\div\frac{5}{7}+\frac{2}{5}+2021\)
\(=\frac{7}{5}+\frac{2}{5}+2021\)
\(=\frac{9}{5}+2021\)
\(=\frac{10114}{5}\)
Số hơi xấu, check lại đề.
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\(a,\left[0,75x+\frac{5}{2}\right]-\frac{4}{7}-\left[-\frac{1}{3}\right]=-\frac{5}{6}\)
\(\Leftrightarrow\left[0,75x+\frac{5}{2}\right]-\frac{4}{7}+\frac{1}{3}=-\frac{5}{6}\)
\(\Leftrightarrow\left[0,75x+\frac{5}{2}\right]=-\frac{5}{6}-\frac{1}{3}+\frac{4}{7}\)
\(\Leftrightarrow0,75x+\frac{5}{2}=-\frac{25}{42}\)
\(\Leftrightarrow0,75x=-\frac{65}{21}\Leftrightarrow x=-\frac{260}{63}\)
\(b,\left[4x-9\right]\left[2,5+-\frac{7}{3}x\right]=0\)
\(\Leftrightarrow\orbr{\begin{cases}4x-9=0\\2,5+-\frac{7}{3}x=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{9}{4}\\x=\frac{15}{14}\end{cases}}\)
Vậy \(x\in\left\{\frac{9}{4};\frac{15}{14}\right\}\)
Tham khảo nhé phamthiminhanh