Đáp án:
`h (x) = (2x)^2 (x^3 - x) - x^2 (4x^3 + 2x - 1) - 1/3x (4x - 12x^2)`
`-> h (x) = 4x^2 (x^3 - x) - 4x^5 - 2x^3 + x^2 - 4/3x^2 + 4x^3`
`-> h (x) = 4x^5 - 4x^3 - 4x^5 - 2x^3 + x^2 - 4/3x^2 + 4x^3`
`-> h (x) = (4x^5 - 4x^5) + (-4x^3 - 2x^3 + 4x^3) + (x^2 - 4/3x^2)`
`-> h (x) = -2x^3 - 1/3x^2`