Câu 1:
(\(\frac{3x}{7}\)\(+\)\(1\))\(\div\)(\(-4\)) \(=-\)\(\frac{1}{28}\)
\(\Leftrightarrow\)\(\frac{3x}{7}\)\(+\)\(1=-\)\(\frac{1}{28}\)\(\times\)(\(-4\))
\(\Leftrightarrow\)\(\frac{3x}{7}\)\(+\)\(1=\)\(\frac{1}{7}\)
\(\Leftrightarrow\)\(\frac{3x}{7}\)\(=\)\(\frac{1}{7}\)\(-1\)
\(\Leftrightarrow\)\(\frac{3x}{7}\)\(=-\)\(\frac{6}{7}\)
\(\Leftrightarrow\)\(x\)\(=-\)\(\frac{6}{7}\)\(\div\)\(\frac{3}{7}\)
\(\Leftrightarrow\)\(x\)\(=\)\(-2\)
\(\left(\frac{3x}{7}+1\right):\left(-4\right)=\frac{-1}{28}\)
\(\frac{3x}{7}+1=\frac{-1}{28}x\left(-4\right)\)
\(\frac{3x}{7}+1=\frac{1}{7}\)
\(\frac{3x}{7}=\frac{1}{7}-1\)
\(\frac{3x}{7}=\frac{-6}{7}\)
=>x=\(\frac{-6}{7}x\frac{7}{3}=-2\)
VẬY X=-2
