a: x^2-4x=0
=>x(x-4)=0
=>\(\left[{}\begin{matrix}x=0\\x-4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=4\end{matrix}\right.\)
b: \(x^2+5x=6\)
=>\(x^2+5x-6=0\)
=>\(x^2+6x-x-6=0\)
=>\(\left(x+6\right)\left(x-1\right)=0\)
=>\(\left[{}\begin{matrix}x+6=0\\x-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-6\\x=1\end{matrix}\right.\)
\(a)x^2-4x=0\\ \Leftrightarrow x\left(x-4\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x-4=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=4\end{matrix}\right.\\ b)x^2+5x=6\\ \Leftrightarrow x^2+5x-6=0\\ \Leftrightarrow x^2-x+6x-6=0\\ \Leftrightarrow x\left(x-1\right)+6\left(x-1\right)=0\\ \Leftrightarrow\left(x-1\right)\left(x+6\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x-1=0\\x+6=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=1\\x=-6\end{matrix}\right.\)
