\(\Leftrightarrow\left[{}\begin{matrix}x=20\\x=-\dfrac{10}{7}\end{matrix}\right.\)
\(\left(x-20\right).\left(7x+10\right)=0\)
\(=>\left[{}\begin{matrix}x-20=0\\7x+10=0\end{matrix}\right.\)
\(=>\left[{}\begin{matrix}x=20\\x=-\dfrac{10}{7}\end{matrix}\right.\)
7x(x-20)+10(x-20)=0
(x-20)x(7x+10)=0
(x-20)=0 hoặc (7x+10)=0
x=20 hoặc 7x=-10
x=20 hoặc x=-10/7