`a,` `x-10=0`
`⇔x=10`
`b,` Thiều đề
`c,` `(x-2)^2-16=0`
`⇔(x-2)^2-4^2=0`
`⇔(x-2-4)(x-2+4)=0`
`⇔(x-6)(x+2)`
\(⇔\left[ \begin{array}{l}x-6=0\\x+2=0\end{array} \right.⇔\left[ \begin{array}{l}x=6\\x=-2\end{array} \right.\)
`d,` `x^3+4x=0`
`⇔x(x^2+4)=0`
\(⇔\left[ \begin{array}{l}x=0\\x^2+4=0\end{array} \right.⇔\left[ \begin{array}{l}x=0\\x^2=-4 \text{(vô lý)}\end{array} \right.\)