b, x^3 + 2x^2 + 2x + 1( ab - 1 )^2 + ( a + b )^2

b) Ta có x³ + 2x² + 2x + 1 = ( x³ + 1 ) + ( 2x² + 2x )

= ( x + 1 )( x² - x + 1 ) + 2x( x + 1 ) = ( x + 1 )( x² + x + 1 )