`a) (2x + 3)(4x^2 - 6x + 9) - 2(4x^3 - 1)`
`= 8x^3 - 12x^2 + 18x + 12x^2 - 18x + 27 - (8x^3 - 2)`
`= 8x^3 - 12x^2 + 18x + 12x^2 - 18x + 27 - 8x^3 + 2`
`= 8x^3 - 8x^3 + 12x^2 - 12x^2 + 18x - 18x + 27 + 2`
`= 29`
`d) (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)`
`= x^3-3x^2+3x-1-x^3-3x^2-3x-1+6x^2-6`
`= (x^3-x^3) + ( -3x^2-3x^2+6x^2)+(3x-3x) +(-1-1-6)`
= -8`
`b)(4x-1)^3-(4x-3)(16x^2+3)`
`=64x^3-48x^2+12x-1-(64x^3+12x-48x^2-9)`
`=64x^3-48x^2+12x-1-64x^3-12x+48x^2+9`
`=8`
`c) 2(x^3 + y^3) - 3(x^2 + y^2) + 30`
`= 2(x + y)(x^2 - xy + y^2) - 3(x^2 + 2xy + y^2 - 2xy) + 30`
`= 2 .1.(x^2 + 2xy + y^2 - 3xy) - 3[ (x + y)^2 - 2xy]+ 30`
`= 2[ (x +y)^2-3xy]-3(1-2xy)+30`
`= 2(1-3xy)-3(-2xy)+30`
`=2(1-3xy)-3(1-2xy)+30`
`=2-6xy-3+6xy+30`
`=-1+30`
`=29`
