`x - 2 = [9x^2 -12x + 4]/[4x^2 + 4x + 1]`

#nhatminhdinh1532#@

Đáp án:

`x-2=\frac{9x^2-12x+4}{4x^2+4x+1}` (`x\ne -1/2`)
`<=> (x-2)(4x^2+4x+1)=9x^2-12x+4`
`<=> (x-2)(4x^2+4x+1)-9x^2+12x-4=0`
`<=> 4x^3+4x^2+x-8x^2-8x-2-9x^2+12x-4=0`
`<=> 4x^3-13x^2+5x-6=0`
`<=> 4x^3-12x^2-x^2+3x+2x-6=0`
`<=> 4x^2(x-3)-x(x-3)+2(x-3)=0`
`<=> (x-3)(4x^2-x+2)=0`
`<=> [(x-3=0),(4x^2-x+2=0):}`
`<=> [(x=3),(4x^2-x=-2):}`
`<=> [(x=3),(x^2-1/4x=-1/2):}`
`<=> [(x=3),(x^2-1/4x+1/64=-1/2+1/64):}`
`<=> [(x=3),((x-1/8)^2=-31/64 \ (\text{Vô nghiệm, } (x-1/8)^2 >=0)):}`
`<=> x=3` (tm)
Vậy `S={3}`