a)
$\text{2x.(4x+12)=0}$
⇒ \(\left[ \begin{array}{l}2x=0\\4x+12=0\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=0\\4x = -12\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=0\\x=-3\end{array} \right.\)
$\text{ Vậy x ∈ {0;-3}}$
b) ${(2-x).(57-19x)=0}$
⇒ \(\left[ \begin{array}{l}2-x=0\\57-19x=0\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=2\\19x=57\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=2\\x=3\end{array} \right.\)
$\text{ Vậy x ∈ {2;3}}$
c) ${x^2-25x=0}$
⇒ ${ x.(x-25)=0}$
⇒ \(\left[ \begin{array}{l}x=0\\x-25=0\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=0\\x=25\end{array} \right.\)
$\text{ Vậy x ∈ {0;25}}$
d) ${ (x^4-81)(-x^2-10)=0}$
⇒ $\{{x^4-81 = 0}$ ${( do -x^2 - 10 < 0 ∀ x )}$
⇒ ${ x^4=81}$
⇒${ x^4=3^4}$
⇒ $\text{ x ∈ {-3;3}}$
e) ${(2x-1)^2=(11-x)^2}$
⇒${ (2x-1)^2-(11-x)^2=0}$
⇒ ${ (2x-1-11+x).(2x-1+11-x)=0}$
⇒${ (3x-12).(x+10)=0}$
⇒ ${ 3.(x-4).(x+10)=0}$
⇒ \(\left[ \begin{array}{l}x-4=0\\x+10=0\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=4\\x=-10\end{array} \right.\)
$\text{ Vậy x ∈ {4;-10}}$
