a) làm gọn hệ số dần: 2x=y
<=>\(\left(2x+3\right)\left(4x^2+3\right)=\) \(\left(y+3\right)\left(y^2+3\right)=-19\)
\(y^3+3y^2+3y+9=-19\Leftrightarrow y^3+3y^2+3y+1=-27\)
\(\Leftrightarrow\left(y+1\right)^3=-3^3\Rightarrow y+1=-3\Rightarrow y=-4\Rightarrow x=-2\)