`a,` `(x-1)(x^2+1)=0`
\(⇒\left[ \begin{array}{l}x-1=0⇒x=1\\x^2+1=0⇒x^2=-1 \text{( vô lý )}\end{array} \right.\)
`Vậy` `S={1}`
`b,` `x/{x-2}+{x-4}/{x-2}={x+2}/x` `(x\ne0;2)`
`⇒{2x-4}/{x-2}={x+2}/x`
`⇒{2x^2-4x}/{x(x-2)}={(x+2)(x-2)}/{x(x-2)}`
`⇒2x^2-4x=x^2-4`
`⇒2x^2-4x-x^2+4=0`
`⇒x^2-4x+4=0`
`⇒(x-2)^2=0`
`⇒x-2=0`
`⇒x=2` `\text{( vô lý )`
`⇒x∈∅`