\(x^4-8x^2+16=8x^2-16x+8\)
\(\Leftrightarrow\left(x^2-4\right)^2=8\left(x-1\right)^2\)
\(\Leftrightarrow\orbr{\begin{cases}x^2-4=2\sqrt{2}\left(x-1\right)\\4-x^2=2\sqrt{2}\left(x-1\right)\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x^2-2\sqrt{2}x-4+2\sqrt{2}=0\\x^2+2\sqrt{2}x-2\sqrt{2}-4=0\end{cases}}\)
Đến đây dễ rồi nhé :P