Đáp án:
$(x+1)²=(2x+3)²$
⇔\(\left[ \begin{array}{l}x+1=2x+3\\x+1=-2x-3\end{array} \right.\)
⇔\(\left[ \begin{array}{l}2x-x=1-3\\x+2x=-3-1\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=-2\\3x=-4\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=-2\\x=-4/3\end{array} \right.\)