Jawabanmu

2014-05-11T20:51:29+07:00
1/s' + 1/s = -1/f
1/6 + 1/15 = -1/f
5/30 + 2/30 = -1/f
7/30 = -1/f
-7f=30
f=-4,28

M=s'/s=6/15=-0,4