Đáp án:
a)\(\left[ \begin{array}{l}x=-1\\x=3\end{array} \right.\)
b)\(\left[ \begin{array}{l}x=-2\\x=7\end{array} \right.\)
Giải thích các bước giải:
$a)x^2-9=2x-6$
$⇒x^2-2x-3=0$
$⇔x^2+x-3x-3=0$
$⇔x.(x+1)-3.(x+1)=0$
$⇔(x+1).(x-3)=0$
⇔\(\left[ \begin{array}{l}x=-1\\x=3\end{array} \right.\)
$b)x^2-5x-14=0$
$⇔x^2-7x+2x-14=0$
$⇔x.(x-7)+2.(x-7)=0$
$⇔(x-7).(x+2)=0$
⇔\(\left[ \begin{array}{l}x=-2\\x=7\end{array} \right.\)
