Đáp án:
$\text{1/ x(x+7)=0 }$
$\text{⇔\(\left[ \begin{array}{l}x=0\\x+7=0\end{array} \right.\) }$
$\text{⇔\(\left[ \begin{array}{l}x=0\\x=-7\end{array} \right.\) }$
$\text{Vậy x ∈ { 0 ; -7} }$
$\text{2/ (x+12).(x-3)=0 }$
$\text{⇔\(\left[ \begin{array}{l}x+12=0\\x-3=0\end{array} \right.\) }$
$\text{⇔\(\left[ \begin{array}{l}x=-12\\x=3\end{array} \right.\) }$
$\text{Vậy x ∈ { -12 ; 3} }$
$\text{ 3/ (-x + 5).(3 – x ) = 0 }$
$\text{⇔\(\left[ \begin{array}{l}-x+5=0\\3-x=0\end{array} \right.\) }$
$\text{⇔\(\left[ \begin{array}{l}x=5\\x=3\end{array} \right.\) }$
$\text{Vậy x ∈ { 5 ; 3} }$
$\text{4 / x.(2 + x).( 7 – x) = 0 }$
$\text{⇔ x = 0 }$
⇔\(\left[ \begin{array}{l}2+x=0\\7-x=0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=-2\\x=7\end{array} \right.\)
$\text{Vậy x ∈ { 0 ; -2 ; 7} }$
$\text{5/ (x - 1).(x +2).(-x -3) = 0 }$
$\text{⇔ x - 1= 0 ⇔ x = 1}$
$\text{⇔ x + 2= 0 ⇔ x = -2 }$
$\text{⇔ -x - 3 =0 ⇔ x = -3 }$
$\text{Vậy x ∈ { 1 ; -2 ; -3} }$
