Factoring the polynomial $6a^4 + a^3b +5a^2b^2 + ab^3 - b^4$ 
can you help me factoring the following polynomial?
$6a^4 + a^3b +5a^2b^2 + ab^3 - b^4$
I don't know where to start from.

Regroup first,
\begin{align}
  (6a^4+5a^2b^2-b^4)+(a^3b+ab^3) &= (6a^2-b^2)(a^2+b^2)+ab(a^2+b^2) \\
  &= (6a^2+ab-b^2)(a^2+b^2) \\
  &= (3a-b)(2a+b)(a^2+b^2)
\end{align}
