Question

\(18x^2-18x+5=3\sqrt[3]{9x^2-9x+2}\)

Answer 1

Đặt \(\sqrt[3]{9x^2-9x+2}=a\) ta được:

\(2a^3+1=3a\Leftrightarrow2a^3-3a+1=0\)

\(\Leftrightarrow\left(a-1\right)\left(2a^2+2a-1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}a=1\\a=\frac{-1+\sqrt{3}}{2}\\a=\frac{-1-\sqrt{3}}{2}\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}9x^2-9x+2=1\\9x^2-9x+2=\left(\frac{-1+\sqrt{3}}{2}\right)^3\\9x^2-9x+2=\left(\frac{-1-\sqrt{3}}{2}\right)^3\end{matrix}\right.\)

Pt bậc 2 xấu quá