`a, (2x + 3)(4x^2 - 6x + 9) - 2(4x^3 - 1)`
`= 8x^3 - 12x^2 + 18x + 12x^2 - 18x + 27 - 8x^3 + 2`
`= 29`
`b, (4x - 1)^3 - (4x - 3)(16x^2 + 3)`
`= 64x^3 - 48x^2 + 12x - 1 - 64x^3 - 12x + 48x^2 + 9`
`= 8`
`c, (x + 1)^3 - (x - 1)^3 - 6(x + 1)(x - 1)`
`= x^3 + 3x^2 + 3x + 1 - x^3 + 3x^2 - 3x + 1 - 6(x^2 - 1)`
`= 2 + 6x^2 - 6x^2 + 6`
` = 8`