Đáp án + Giải thích các bước giải:
Ta có :
`1)x.(x+7)=0`
`→` \(\left[ \begin{array}{l}x=0\\x+7=0\end{array} \right.\)
`→` \(\left[ \begin{array}{l}x=0\\x=-7\end{array} \right.\)
Vậy `x∈{0;-7}`
`2)(x+12).(x-3)=0`
`→` \(\left[ \begin{array}{l}x+12=0\\x-3=0\end{array} \right.\)
`→` \(\left[ \begin{array}{l}x=-12\\x=3\end{array} \right.\)
Vậy `x∈{-12;3}`
`3)(-x+5).(3-x)=0`
`→` \(\left[ \begin{array}{l}-x+5=0\\3-x=0\end{array} \right.\)
`→` \(\left[ \begin{array}{l}-x=-5\\x=3\end{array} \right.\)
`→` \(\left[ \begin{array}{l}x=5\\x=3\end{array} \right.\)
Vậy `x∈{5;3}`
`4)x.(2+x).(7-x)=0`
`→` \(\left[ \begin{array}{l}x=0\\2+x=0\\7-x=0\end{array} \right.\)
`→` \(\left[ \begin{array}{l}x=0\\x=-2\\x=7\end{array} \right.\)
Vậy `x∈{0;-2;7}`
`5)(x-1).(x+2).(-x-3)=0`
`→` \(\left[ \begin{array}{l}x-1=0\\x+2=0\\-x-3=0\end{array} \right.\)
`→` \(\left[ \begin{array}{l}x=1\\x=-2\\-x=3\end{array} \right.\)
`→` \(\left[ \begin{array}{l}x=1\\x=-2\\x=-3\end{array} \right.\)
Vậy `x∈{1;-2;-3}`
