\(a,3x^3-12x=0\)
\(\Rightarrow3x\left(x^2-4\right)=0\)
\(\Rightarrow3x\left(x-2\right)\left(x+2\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}3x=0\\x-2=0\\x+2=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x=2\\x=-2\end{matrix}\right.\)
\(b,2x^2-x-6=0\)
\(\Rightarrow2x^2-4x+3x-6=0\)
\(\Rightarrow\left(2x^2-4x\right)+\left(3x-6\right)=0\)
\(\Rightarrow2x\left(x-2\right)+2\left(x-2\right)=0\)
\(\Rightarrow\left(x-2\right)\left(2x+2\right)=0\)
\(\Rightarrow2\left(x-2\right)\left(x+1\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x-2=0\\x+1=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=2\\x=-1\end{matrix}\right.\)
a) 3x3-12x=0
3x(x2-4)=0
3x(x-2)(x+2)=0
\(\Rightarrow\left[{}\begin{matrix}3x=0\\x-2=0\\x+2=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=2\\x=-2\end{matrix}\right.\)
Vậy x=0,2 hoặc -2
b)2x2-x-6=0
2x2+3x-4x-6=0
(2x2+3x)-(4x+6)=0
x(2x+3)-2(2x+3)=0
(2x+3)(x-2)=0
\(\Rightarrow\left[{}\begin{matrix}2x+3=0\\x-2=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}2x=-3\\x=2\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{-3}{2}\\x=2\end{matrix}\right.\)
Vậy x =-3/2 hoặc 2