Answer
$$\frac{1}{3}$$
Work Step by Step
\begin{aligned}
\int_{-\infty}^{0} e^{3 x} d x &=\lim _{R \rightarrow-\infty} \int_{R}^{0} e^{3 x} d x \\
&=\lim _{R \rightarrow-\infty} \left.\frac{e^{3 x}}{3}\right|_{R} ^{0} \\
&=\lim _{R \rightarrow-\infty} \frac{1}{3}-\frac{e^{3 R}}{3}\\
&=\frac{1}{3} \end{aligned}
Converges.
