4)а^3-b^3+a^2-b^2 5)х^4+ху^3-х^3у-у^4 6)а^4-а^3b+ab^3-b^4 представьте в виде произведения...

Решите задачу:

$4)(a - b) \times ( {a}^{2} + ab + {b}^{2} ) + (a - b) \times (a + b) = (a - b) \times ( {a}^{2} + ab + {b}^{2} + a + b)$

$5)x( {x}^{3} + {y}^{3} ) - y( {x}^{3} + {y}^{3} ) = (x - y) \times ( {x}^{3} + {y}^{3} ) = (x - y) \times (x + y) \times ( {x}^{2} + xy + {y}^{2} )$

$6) {a}^{3} (a - b) + {b}^{3} (a - b) = ( {a}^{3} + {b}^{3} ) \times (a - b) = (a + b) \times (a - b) \times ( {a}^{2} + ab + {b}^{2} )$