$1)x(x+7)=0$
`=>`\(\left[ \begin{array}{l}x=0\\x+7=0\end{array} \right.\) `=>`\(\left[ \begin{array}{l}x=0\\x=-7\end{array} \right.\)
$2)(x+12)(x-3)=0$
`=>`\(\left[ \begin{array}{l}x+12=0\\x-3=0\end{array} \right.\) `=>`\(\left[ \begin{array}{l}x=-12\\x=3\end{array} \right.\)
$3)(-x+5)(3-x)=0$
`=>`\(\left[ \begin{array}{l}-x+5=0\\3-x=0\end{array} \right.\) `=>`\(\left[ \begin{array}{l}x=5\\x=3\end{array} \right.\)
$4)x(2+x)(7-x)=0$
`=>`\(\left[ \begin{array}{l}2+x=0\\7-x=0\end{array} \right.\) `=>`\(\left[ \begin{array}{l}x=-2\\x=7\end{array} \right.\)
$5)(x-1)(x+2)(-x-3)=0$
`=>`\(\left[ \begin{array}{l}x-1=0\\x+2=0\\-x-3=0\end{array} \right.\) `=>`\(\left[ \begin{array}{l}x=1\\x=-2\\x=-3\end{array} \right.\)
