1) ở đây : https://hoc24.vn/hoi-dap/question/637404.html
2) pt \(\Leftrightarrow\left(9x^2+18x-16\right)\left(x^2+2x+1\right)=-16\)
\(\Leftrightarrow9x^4+36x^3+29x-14x=0\)
\(\Leftrightarrow x\left(9x^3+18x^2+18x^2+36x-7x-14\right)=0\)
\(\Leftrightarrow x\left(9x^2\left(x+2\right)+18x\left(x+2\right)-7\left(x+2\right)\right)=0\)
\(\Leftrightarrow x\left(x+2\right)\left(9x^2+18x-7\right)=0\)
\(\Leftrightarrow x\left(x+2\right)\left(9x^2-3x+21x-7\right)=0\)
\(\Leftrightarrow x\left(x+2\right)\left(3x\left(3x-1\right)+7\left(3x-1\right)\right)=0\)
\(\Leftrightarrow x\left(x+2\right)\left(3x+7\right)\left(3x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-2\\x=\dfrac{-7}{3}\\x=\dfrac{1}{3}\end{matrix}\right.\) vậy ............................................................................................................
