Trả lời:
a) \(x\left(x-3\right)+2x-6=0\Leftrightarrow x\left(x-3\right)+\left(2x-6\right)=0\Leftrightarrow x\left(x-3\right)+2\left(x-3\right)=0\Leftrightarrow\left(x+2\right)\left(x-3\right)=0\Leftrightarrow\left[{}\begin{matrix}x+2=0\\x-3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=3\end{matrix}\right.\)b) \(x^2+7x-2\left(x+7\right)=0\Leftrightarrow\left(x^2+7x\right)-2\left(x+7\right)=0\Leftrightarrow x\left(x+7\right)-2\left(x+7\right)=0\Leftrightarrow\left(x-2\right)\left(x+7\right)=0\Leftrightarrow\left[{}\begin{matrix}x-2=0\\x+7=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-7\end{matrix}\right.\)