\[3uv^{3} + u^{2}v^{2} - 2uv^{3} + u^{3}v - u^{4} =\]
\[= uv^{3} + u^{2}v^{2} + u^{3}v - u^{4};\ \]
\[u = 1;\ v = 1:\]
\[1 \cdot ( - 1)^{3} + 1^{2} \cdot ( - 1)^{2} + 1^{3} \cdot ( - 1) - 1^{4} =\]
\[= - 1 + 1 - 1 - 1 = - 2.\]