`1)`
`(x - 2)^3 - (x - y)(x + y) - x^3 - y^2 + 5x`
`= x^3 - 6x^2 + 12x - 8 - x^2 + y^2 - x^3 - y^2 + 5x`
`= -7x^2 + 17x - 8 `
`2)`
`a)`
`x^2(x - y) + y(x^2 - 1) = -y - x + x^3`
`⇔ x^3 - x^2y + x^2y - y + y + x - x^3 = 0`
`⇔ x = 0`
`b)`
`x(x - 3) - 3x + 9 = 0`
`⇔ x(x - 3) - 3(x - 3) = 0`
`⇔ (x - 3)^2 = 0`
`⇔ x = 3`