`(2x-1)(x+7)=x^2 -49`
`⇔(2x-1)(x+7)=(x-7)(x+7)`
`⇔(2x-1)(x+7)-(x-7)(x+7)=0`
`⇔(x+7)(2x-1-x+7)=0`
`⇔(x+7)(x+6)=0`
`⇔`\(\left[ \begin{array}{l}x+7=0\\x+6=0\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=-7\\x=-6\end{array} \right.\)
$\color{black}{\huge\text{xin hay nhất }}$