`a)`
`2 (x^3 - 1)-2x^2 (x+2x^4) + (4x^5 + 4)x = 6`
`=> 2 . x^3 - 2 . x - 2x^2 . x - 2x^2 . 2x^4 + 4x^5 . x + 4 . x = 6`
`=> 2x^3 - 2 - 2x^3 - 4x^6 + 4x^6 + 4x = 6`
`=> (4x^6 - 4x^6) + (2x^3 - 2x^3) + 4x - 2 = 6`
`=> 4x - 2 = 6`
`=> 4x = 8`
`=> x = 2`
Vậy `x=2`
`b)`
`(2x)^2 (4x-2) - (x^3 - 8x^2) = 15`
`=> 4x^2 (4x-2) - x^3 + 8x^2 = 15`
`=> 4x^2 .4x - 4x^2 . 2 - x^3 + 8x^2 = 15`
`=> 16x^3 - 8x^2 - x^3 + 8x^2 = 15`
`=> (16x^3 - x^3) + (8x^2 - 8x^2) =15`
`=> 15x^3=15`
`=> x^3 = 1`
`=> x = 1`
Vậy `x=1`
