Question

x^3 -27 = -3*x*(x-3)

Answer 1

\(x^3-27=-3x\left(x-3\right)\\ \left(x-3\right)\left(x^2+3x+9\right)+3x\left(x-3\right)=0\\ \left(x-3\right)\left(x^2+3x+9+3x\right)=0\\ \left(x-3\right)\left(x^2+6x+9\right)=0\\ \left(x-3\right)\left(x+3\right)^2=0\\ \left[{}\begin{matrix}x-3=0\\x+3=0\end{matrix}\right.\left[{}\begin{matrix}x=3\\x=-3\end{matrix}\right.\)

Answer 2

=>(x-3)(x^2+3x+9)+3x(x-3)=0

=>(x-3)(x+3)^2=0

=>x=3 hoặc x=-3