C1
Cho `2x^2-4x+2=0`
`<=>2.(x^2-2x+1)=0`
`<=>x^2-2x+1=0`
`<=>x^2-x-x+1=0`
`<=>x.(x-1)-(x-1)=0`
`<=>(x-1).(x-1)=0`
`<=>(x-1)^2=0`
`<=>x-1=0<=>x=1`
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C2
`2x^2-4x+2=0`
`<=>2x^2-2x-2x+2=0`
`<=>2x(x-1)-2.(x-1)=0`
`<=>(2x-2).(x-1)=0`
`<=>2.(x-1).(x-1)=0`
`<=>(x-1)^2=0`
`<=>x-1=0<=>x=1`
Vậy đa thức có nghiệm `x=1`