`a)`
`(x+4)(x^2 - 4x + 16) - x (x-5)(x+5) = 264`
`=> (x+4)(x^2 - x . 4 + 4^2) - x (x^2 - 5^2) = 264`
`=> (x^3 + 4^3) - x (x^2 - 25) = 264`
`=> x^3 + 64 - x^3 + 25x = 264`
`=> 25x + 64 = 264`
`=> 25x = 200`
`=> x = 8`
Vậy `x=8`
`b)`
`(x-2)^3 - (x-2)(x^2 + 2x+4) + 6 (x-2)(x+2) = 60`
`=> (x^3 - 3 . x^2 . 2 + 3 . x . 2^2 - 2^3) - (x^3 - 2^3) + 6 (x^2 - 2^2) =60`
`=> (x^3 - 6x^2 + 12x - 8) - (x^3- 8) + 6 (x^2 - 4) =60`
`=> x^3 - 6x^2 + 12x - 8 - x^3 + 8 + 6x^2 -24 =60`
`=> (x^3 - x^3) + (6x^2 - 6x^2) + 12x + ( 8 -8-24) = 60`
`=> 12x - 24 = 60`
`=> 12x = 84`
`=> x = 7`
Vậy `x=7`
