Jawabanmu

2014-05-15T18:55:29+07:00
F=60 cm
s= 30cm
1/s'= 1/s-1/f
= 2/60-1/60
=1/60
s'=60/1
2014-05-15T18:58:17+07:00
M = 120 cm 
f = 1/2 M= 60 cm
s= 30 cm

\frac{1}{s'} = \frac{1}{f} - \frac{1}{s}
                  =  \frac{1}{60} -  \frac{1}{30}
 \frac{1}{s'}  =  \frac{1}{30}
s' = 30 cm