\[2a^{2} + 3a - 2 + 5a^{3} - 3a + 2 =\]
\[= 5a^{3} + 2a^{2}.\]
\[2a^{2} + 3a - 2 - \left( 5a^{3} - 3a + 2 \right) =\]
\[= 2a^{2} + 3a - 2 - 5a^{3} + 3a - 2 =\]
\[= - 5a^{3} + 2a^{2} + 6a - 4.\]