Giải thích các bước giải :

`+)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∈{-7; 0}`

`+)(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}`

`+)(-x+5)(3-x)=0`

`<=>`\(\left[ \begin{array}{l}-x+5=0\\3-x=0\end{array} \right.\)

`<=>`\(\left[ \begin{array}{l}x=5\\x=3\end{array} \right.\)

Vậy : `x∈{3; 5}`

`+)x(x+2)(7-x)=0`

`<=>`\(\left[ \begin{array}{l}x=0\\x+2=0\\7-x=0\end{array} \right.\)

`<=>`\(\left[ \begin{array}{l}x=0\\x=-2\\x=7\end{array} \right.\)

Vậy : `x∈{-2; 0; 7}`

`+)(x-1)(x+2)(-x-3)=0`

`<=>`\(\left[ \begin{array}{l}x-1=0\\x+2=0\\-x-3=0\end{array} \right.\)

`<=>`\(\left[ \begin{array}{l}x=1\\x=-2\\x=-3\end{array} \right.\)

Vậy : `x∈{-3; -2; 1}`

Đáp án + Giải thích các bước giải:

`x.(x+7)=0 `

\(\left[ \begin{array}{l}x=0\\x+7=0\end{array} \right.\) 

\(\left[ \begin{array}{l}x=0\\x=-7\end{array} \right.\)

$$$$

`(x+12).(x-3)=0`

\(\left[ \begin{array}{l}x+12=0\\x-3=0\end{array} \right.\)

\(\left[ \begin{array}{l}x=-12\\x=3\end{array} \right.\)

$$$$

`(-x+5).(3-x)=0`

`( x - 5 ) . ( 3 - x ) = 0 `

\(\left[ \begin{array}{l}x-5=0\\3 -x=0\end{array} \right.\)

\(\left[ \begin{array}{l}x=5\\x=3\end{array} \right.\)

$$$$

`x(2+x)(7-x)=0`

\(\left[ \begin{array}{l}x= 0\\2+x=0\\7-x=0\end{array} \right.\)

\(\left[ \begin{array}{l}x=0\\x=-2\\x=7\end{array} \right.\)

$$$$

`(x-1).(x+2).(-x-3)=0`

\(\left[ \begin{array}{l}x - 1 = 0\\x+2=0\\ -x -3 =0\end{array} \right.\) 

\(\left[ \begin{array}{l}x =1\\x=-2\\x=-3\end{array} \right.\)