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`5x - 3x^2 + 3x^3 - x^4=(x+1)^2`

`⇔ 5x - 3x^2 + 3x^3 - x^4-x^2-2x-1=0`

`⇔ -x^4 + 3x^3 - 4x^2 + 3x - 1=0`

`⇔ -x^4 + x^3  + 2x^3 - 2x^2 - 2x^2 + 2x + x - 1=0`

`⇔ -x^3(x-1) + 2x^2(x-1) - 2x(x-1) + x-1=0`

`⇔ (x-1)(-x^3 + 2x^2 - 2x + 1)=0`

`⇔ (x-1)(-x^3 + x^2 + x^2 - x - x +1)=0`

`⇔ (x-1)[-x^2(x-1) + x(x-1) - x+1]=0`

`⇔ (x-1)^2(-x^2+x-1)=0`

`⇔ (x-1)^2[(x-1/2)^2 + 3/4]=0`

Vì `(x-1/2)^2 + 3/4 >0`

Để `(x-1)^2[(x-1/2)^2 + 3/4]=0`

`⇒ x-1=0`

`⇔ x=1`

Vậy,..

`color{purple}{@SHIN}`