Question

Solve:
$\frac{1}{f}=\frac{1}{u}+\frac{1}{v}$, find $u$, if $v=32cm,f=16cm$

Answer 1

$\begin{array}{c}\frac{1}{f}=\frac{1}{v}+\frac{1}{u},ifv=32,f=16,u=?\\ \Rightarrow \frac{1}{16cm}=\frac{1}{u}+\frac{1}{32cm}\\ \Rightarrow \frac{1}{16}-\frac{1}{32}=\frac{1}{u}\\ \Rightarrow \frac{\left(2-1\right)cm}{32}=\frac{1}{u}\\ \Rightarrow \frac{1}{32cm}=\frac{1}{u}\\ u=32cm.\end{array}$