Transcript text: Let $f$ be the function
\[
f(x)=\left\{\begin{array}{ll}
3 x^{-1} & \text { for } x<-1 \\
a x+b & \text { for }-1 \leq x \leq \frac{1}{2} \\
4 x^{-1} & \text { for } x>\frac{1}{2}
\end{array}\right.
\]
Find the values of $a$ and $b$ that make the function continuous.
(Use symbolic notation and fractions where needed.)