b, [ 5( x^3 - y^3 )^4 + ( x - y )^3 ]:( x^2 - 2xy + y^2 )

b) Ta có [ 5( x³ - y³ )⁴ + ( x - y )³ ]:( x² - 2xy + y² )

= [ 5( x - y )⁴( x² + xy + y² )⁴ + ( x - y )³ ]:( x - y )²

= 5( x - y )²( x² + xy + y² )⁴ + ( x - y )