gợi ý
\(2x^3+8x^2-3x^2-12x=0\)
\(\left(2x^3+8x^2\right)-\left(3x^2-12x\right)=0\)
\(2x^3+5x^2-12x=0\)
\(\Leftrightarrow\left(2x^3-3x^2\right)+\left(8x^2-12x\right)=0\)
\(\Leftrightarrow2x^2\left(x-\frac{3}{2}\right)+8x\left(x-\frac{3}{2}\right)=0\)
\(\Leftrightarrow\left(2x^2+8x\right)\left(x-\frac{3}{2}\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}2x^2+8x=0\\x-\frac{3}{2}=0\end{cases}}\)
tự túc :)