f = 10 cm, v = -15 cm (same side), u = ?
$\frac{1}{f}$ = $\frac{1}{u}$ + $\frac{1}{v}$
$\frac{1}{u}$ = $\frac{1}{10}$ - $\frac{1}{-15}$
= $\frac{-3 - -2}{-30}$ = $\frac{1}{6}$
= 6 cm
johnmulu answered the question on February 18, 2017 at 08:57
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