Answer
$$f(x)= x^2+x-6$$
Work Step by Step
Given Slope$=2x+1$ and passes through $(-3,0)$
Since the curve is given by
\begin{align*}
f(x)&=\int (2x+1)dx\\
&=x^2+x+c
\end{align*}
Since the curve passes through $(-3,0)$, then $c= -6$ and
$$f(x)= x^2+x-6$$
