\[\boxed{\text{607\ (607).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ 3x^{3} - 2x^{2} - x + 4 =\]
\[= \left( 3x^{3} + 4 \right) + ( - 2x^{2} - x)\]
\[\textbf{б)} - 5y^{4} + 4y^{3} + 3y^{2} - 2y =\]
\[= \left( 3y^{2} - 5y^{4} \right) + (4y^{3} - 2y)\]