Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

$-3a^3+12a^2+a+1$
Removing the grouping symbols, then the given expression, $(3+5a+3a^2-a^3)-(2+4a-9a^2+2a^3)$, is equivalent to \begin{array}{l} 3+5a+3a^2-a^3-2-4a+9a^2-2a^3 .\end{array} By combining like terms, then \begin{array}{l} (-a^3-2a^3)+(3a^2+9a^2)+(5a-4a)+(3-2) \\\\= -3a^3+12a^2+a+1 .\end{array}