`a)x^3-x=0`
`<=>x(x^2-1)=0`
`<=>[(x=0),(x^2-1=0<=>x^2=1<=>x=+-1):}`
Vậy `S={0;+-1}`
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`b)x^3-2x^2+x=0`
`<=>x(x^2-2x+1)=0`
`<=>x(x-1)^2=0`
`<=>[(x=0),((x-1)^2=0<=>x=1):}`
Vậy `S={0;1}`
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`c)x^3-4x^2+3x=0`
`<=>x(x^2-4x+3)=0`
`<=>x(x^2-3x-x+3)=0`
`<=>x[x(x-3)-(x-3)]=0`
`<=>x(x-3)(x-1)=0`
`<=>[(x=0),(x=3),(x=1):}`
Vậy `S={0;1;3}`
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