`a) x ( x - 2 ) = 0`
`→` \(\left[ \begin{array}{l}x=0\\x-2=0\end{array} \right.\)
`→` \(\left[ \begin{array}{l}x=0\\x=2\end{array} \right.\)
Vậy `x∈{0;2}`
`b)x ( x + 7 ) = 0`
`→` \(\left[ \begin{array}{l}x=0\\x+7=0\end{array} \right.\)
`→` \(\left[ \begin{array}{l}x=0\\x=-7\end{array} \right.\)
Vậy `x∈{0;-7}`
`c)( x - 3 ) ( x^2 + 12 ) = 0`
`x^2+12≥12`
`→x-3=0`
`→x=3`
Vậy `x=3`
`d)( x - 1) ( x^2 - 4 ) = 0`
`→` \(\left[ \begin{array}{l}x-1=0\\x^2-4=0\end{array} \right.\)
`→` \(\left[ \begin{array}{l}x=1\\x^2=4\end{array} \right.\)
`→` \(\left[ \begin{array}{l}x=1\\x=±2\end{array} \right.\)
Vậy `x∈{1;2;-2}`
