\[a^{3}b^{2} + ab^{2} + a^{2}b^{4} + \ *\]
\[*\ = - a^{2}b^{4}:\]
\[a^{3}b^{2} + ab^{2} + a^{2}b^{4} - a^{2}b^{4} =\]
\[= a^{3}b^{2} + ab^{2}.\]