`2(x^{2}+1/x^{2})-3(x+1/x)+2=0(x ne 0)`
`<=>2(x^{2}+2+1/x^{2})-3(x+1/x)-2=0`
`<=>2(x+1/x)^{2}-3(x+1/x)-2=0`
Đặt `x+1/x=a`
`pt<=>2a^{2}-3a-2=0`
`Delta=9+16=25`
`=>sqrtDelta=5`
`=>a_1=(3+5)/4=2,a_2=(3-5)/4=-1/2`
`+)a=2`
`<=>x+1/x=2`
`<=>x^{2}+1=2x`
`<=>x^{2}-2x+1=0`
`<=>(x-1)^{2}=0`
`<=>x=1(tm)`
`+)a=-1/2`
`<=>x+1/x=-1/2`
`<=>2x^{2}+2=-x`
`<=>2x^{2}-x+2=0`
`Delta=1-1=-15<0`
`=>` pt vô nghiệm.
Vậy `S={1}`.
