\(c,x\left(\dfrac{1}{5}+\dfrac{1}{4}\right)-\left(\dfrac{1}{7}+\dfrac{1}{8}\right)=0\\ \Leftrightarrow\dfrac{9}{20}x-\dfrac{15}{56}=0\\ \Leftrightarrow x=\dfrac{15}{56}\cdot\dfrac{20}{9}=\dfrac{25}{42}\)
\(d,\left(2x-\dfrac{2}{3}\right)\left(x+0,5\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}2x=\dfrac{2}{3}\\x=-\dfrac{1}{2}\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{3}\\x=-\dfrac{1}{2}\end{matrix}\right.\)
\(4,\)
\(\left(-111\right):\left(-\dfrac{1}{11}\right)=1221\)
d: Ta có: \(\left(2x-\dfrac{2}{3}\right)\left(x+\dfrac{1}{2}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}2x=\dfrac{2}{3}\\x=-\dfrac{1}{2}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{3}\\x=-\dfrac{1}{2}\end{matrix}\right.\)
c. \(x\left(\dfrac{1}{5}+\dfrac{1}{4}\right)-\left(\dfrac{1}{7}+\dfrac{1}{8}\right)=0\)
<=> \(x\left(\dfrac{1}{5}+\dfrac{1}{4}\right)=\dfrac{1}{7}+\dfrac{1}{8}\)
<=> \(x.\dfrac{9}{20}=\dfrac{15}{56}\)
<=> x = \(\dfrac{15}{56}:\dfrac{9}{20}\)
<=> x = \(\dfrac{25}{42}\)
d. \(\left(2x-\dfrac{2}{3}\right)\left(x+0,5\right)=0\)
<=> \(\left[{}\begin{matrix}2x-\dfrac{2}{3}=0\\x+0,5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{3}\\x=-\dfrac{1}{2}\end{matrix}\right.\)
