Jawabanmu

2014-02-19T17:00:59+07:00
Diketahui : s = 15
s' = 2 x s = 30
Ditanya : f
Jawab :
1/f = 1/s + 1/s'
1/f = 1/15 + 1/30
1/f = 2/30 + 1/30
1/f = 3/30
jadi f = 30/3 = 10 cm