`(3x + 6)(9x + 2) - 4 = -4`
`<=> (3x + 6)(9x + 2) = 0`
`<=>` \(\left[ \begin{array}{l}3x + 6 = 0\\9x + 2 = 0\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}3x = -6\\9x = -2\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=-2\\x=\dfrac{-2}{9}\end{array} \right.\)
Vậy `x in {-2; (-2)/9}`