7. Select equivalent expressions AND solve. x^{3}+x^{2}+7 x+7=x+1 \text { A }[x=(-2 i), x=(2 i), x=1] \mathbf{B}[x=-i \sqrt{6}, x=i \sqrt{6}, x=(-1)] \text { C } x^{3}+x^{2}+6 x+6=0 \text { D

}\left(x^{2}-5\right)(x-3)=0 \begin{array}{|l|l} \hline E & \left(x^{2}+6\right)(x+1)=0 \end{array}