As \( t \rightarrow -\infty, f(t) \rightarrow \infty \) and as \( t \rightarrow \infty, f(t) \rightarrow -\infty \). Thus, the final boxed answers are:
\[
\boxed{\text{As } t \rightarrow -\infty, f(t) \rightarrow \infty}
\]
\[
\boxed{\text{As } t \rightarrow \infty, f(t) \rightarrow -\infty}
\]