Rút gọn ( 2x+3 ) . ( 4x^2 - 6x + 9 ) - 2. ( 4x^3 - 1 )

bài4 . rút gọn : a, ( 2x+3 ) . ( 4x^2 - 6x + 9 ) - 2. ( 4x^3 - 1 ) ; b, ( 4x - 1 )^3 - ( 4x - 3 ) . ( 16x^2 + 3 ) ; c, ( x+1 )^3 - ( x-1 )^3 - 6. ( x+1 ) . ( x-2 )