a/ Đặt \(x-3=t\)
\(\left(t+1\right)^4+\left(t-1\right)^4-82=0\)
\(\Leftrightarrow2t^4+12t^2-80=0\)
\(\Leftrightarrow t^4+6t^2-40=0\Rightarrow\left[{}\begin{matrix}t^2=4\\t^2=-10\left(l\right)\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}t=2\\t=-2\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=5\\x=1\end{matrix}\right.\)
b/ \(\Leftrightarrow\left(x^2-4x\right)^2+2\left(x^2-4x+4\right)-43=0\)
Đặt \(x^2-4x=t\)
\(t^2+2\left(t+4\right)-43=0\)
\(\Leftrightarrow t^2+2t-35=0\Rightarrow\left[{}\begin{matrix}t=5\\t=-7\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x^2-4x-5=0\\x^2-4x+7=0\left(vn\right)\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=-1\\x=5\end{matrix}\right.\)
