Answer
$f(x)=\displaystyle \frac{1}{3}x^3+3e^{x}+Cx+D$
Work Step by Step
$\left[\begin{array}{cc}
\text{}f'' & \text{particular antiderivative,}f'\\
2x^{1} & 2\cdot\dfrac{x^{2}}{2}=x^{2} \\
3e^{x} & 3\cdot e^{x}
\end{array}\right]$
$f'(x)=x^{2}+3e^{x}+C$
$\left[\begin{array}{cc}
\text{}f' & \text{particular antiderivative,}f\\
x^{2} & \dfrac{x^{3}}{3}\\
3e^{x} & 3\cdot e^{x} \\
C & Cx
\end{array}\right]$
$f(x)=\displaystyle \frac{1}{3}x^3+3e^{x}+Cx+D$