Tìm x, biết rằng: (x + 3) (x^2 – 3x + 9) – x (x – 2)^2 = 27

* Hướng dẫn giải

$\left(x+3\right)\left(x^2–3x+9\right)–x{\left(x–2\right)}^2=27$

$x^3+27-x\left(x^2-4x+4\right)=27$

$x^3+27-x\left(x^2-4x+4\right)=27$

$4x\left(x-1\right)=0$

$\Rightarrow \left[\begin{array}{l}x=0\\ x-1=0\end{array}\right.$

$\Rightarrow \left[\begin{array}{l}x=0\\ x=1\end{array}\right.$

Vậy $x\in \left\{0;1\right\}$