$\text{a)}\left(x^3-6x^2+12x-16\right):\left(x-4\right)=x^2-2x+4$  

 

$\text{b)}\left(x^3-x^2-5x+21\right):\left(x+3\right)=x^2-4x+7$  

 

$\text{c)}\left(x^3-3x^2+3x-2\right):\left(x-2\right)=x^2-x+1$  

 

$\text{d)}\left(x^4+5x^3-12x^2+5x+1\right):\left(x-1\right)=x^3+6x^2-6x-1$