Bài 3nhân tung sắp xếp ta đc
$\sqrt{(3x+1)^3}+\sqrt{3x+1}-x^3-3x^2-4x-2=0$
$\Leftrightarrow \sqrt{(3x+1)^3}-8+\sqrt{3x+1}-2-x^3-3x^2-4x+8=0$
$\Leftrightarrow \frac{9(x-1)(3x^2+6x+7)}{\sqrt{(3x+1)^3}+8}+\frac{3(x-1)}{\sqrt{3x+1}+2}-(x-1)(x^2+4x+8)=0$