[TEX]x^{3}+5x^{2}+3x-9=0[/TEX]
[TEX]<=>x^{3}-x^{2}+6x^{2}-6x+9x-9=0[/TEX]
[TEX]<=>x^{2}(x-1)+6x(x-1)+9(x-1)=0[/TEX]
[TEX]<=>(x-1)(x^{2}+6x+9)=0[/TEX]
[TEX]<=>(x-1)(x+3)^{2}=0[/TEX]
[TEX]<=>x-1=0[/TEX] hoặc [TEX]x+3=0[/TEX]
[TEX]<=>x=1[/TEX] hoặc [TEX]x=-3[/TEX]