`#tnvt`
`a)(x-2)(x^2-3x-4)-(x^3+5x^2-x)=0`
`<=>x^3-3x^2-4x-2x^2+6x+8-x^3-5x^2+x=0`
`<=>(x^3-x^3)+(-3x^2-2x^2-5x^2)+(-4x+6x+x)+8=0`
`<=>-10x^2+3x+8=0`
`<=>-10.x^2+2.10.x. 3/20-10. 9/400+10 .329/400=0`
`<=>(x-3/20)^2-89/100=0`
`<=>(x-3/20-(\sqrt{329})/20)(x-3/20+\frac{\sqrt{329}}{20})=0`
`<=>[(x=\frac{\sqrt{329}+3}{20}),(x=\frac{-\sqrt{329}+3}{20}):}`
Vậy `x\in{\frac{+-\sqrt{329}+3}{20}}`
