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