[tex]A(x)=x^4+2x^3-x^2-2x\\
A(x)=x^3(x+2)-x(x+2)\\
A(x)=(x+2)(x^3-x)\\
A(x)=x(x+2)(x^2-1)\\
A(x)=x(x+2)(x-1)(x+1)\\
Cei\ patru\ termeni\ sunt\ consecutivi\Rightarrow A\vdots 4\ (1)\\
Dar\ si\ x(x+1)\ sunt\ termeni\ consecutivi\Rightarrow A\vdots 2\ (2)\\
Din\ (1)\ si\ (2)\Rightarrow A\vdots 8\\[/tex]