Answer
$i=-12cm$
Work Step by Step
We can use the given values in equation 34-9 to find the image distance, $i$.
$\frac{1}{p}+\frac{1}{i}=\frac{1}{f}$
Solving for $i$, we have:
$i=(\frac{1}{f}-\frac{1}{p})^{-1}$
$i=(\frac{1}{-30cm}-\frac{1}{20cm})^{-1}$
$i=-12cm$
