`(x^2-4x+5)^2-(x-1)(x-3)=4`
`⇔(x^2-4x+5)^2-(x^2-4x+5)=2`
`⇔(x^2-4x+4)(x^2-4x+5)=2`
đặt` : x^2-4x+4=a`
`⇔a(a+1)=2`
`⇔a^2+a-2=0`
`⇔(a+2)(a-1)=0`
`⇔`\(\left[ \begin{array}{l}a=-2\\a=1\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x^2-4x+4=-2\\x^2-4x+4=1\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}(x-2)^2=-2(loại)\\(x-2)^2=1\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x-2=1\\x-2=-1\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=3\\x=1\end{array} \right.\)
