Jawabanmu

2014-06-05T22:18:46+07:00
Diket = So =15 cm, M = 2
ditanya = R
jawab = M = Si/So
Si = M × So = 2×15 = 30 cm
1/f = 1/15 + 1/30
= 2/30 + 1/30 = 3/30
f = 30/3 = 10 cm
R = 2 × f = 2×10 = 20 cm

maaf kalau salah