`a) (x + 2)^3 - (x + 1)^3 `

`= [(x + 2) - (x + 1)] xx [(x + 2)^2 + (x + 2)(x + 1) + (x + 1)^2] `

`= 1 xx [(x + 2)^2 + (x + 2)(x + 1) + (x + 1)^2] `

`= 1 xx [x^2 + 4x + 4 + x^2 + 3x + 2 + x^2 + 2x + 1] `

`= 1 xx [3x^2 + 9x + 7] `

`= 3x^2 + 9x + 7`

`b) (x - 3)^2 - 5(x - 3)^2 `

`= (1 - 5)(x - 3)^2`

`= -4(x - 3)^2 `

`c) (x + 1)^3 - x^2(x + 1) - 2x(x + 2) `

`= x^3 + 3x^2 + 3x + 1 - x^3 - x^2 - 2x^2 - 4x `

`= (x^3 - x^3) + (3x^2 - x^2 - 2x^2) + (3x - 4x) + 1 `

`= 0 + 0 - x + 1`

`= -x + 1`