\(VT=-2x^2+6x-12\)
\(VT=-2\left(x^2-3x+6\right)\)
\(VT=-2\left(x^2-3x+\dfrac{9}{4}+\dfrac{15}{4}\right)\)
\(VT=-2\left(x^2-3x+\dfrac{9}{4}\right)-\dfrac{15}{4}.2\)
\(VT=-2\left(x-\dfrac{3}{2}\right)^2-\dfrac{15}{2}< 0=VP\)
Vậy phương trình vô nghiệm(đpcm)