Jawabanmu

2014-05-23T10:33:35+07:00
1/f = 1/So + 1/si
|M| = |Si/So|
F = 20
M = 2X
Si = 2 So
1/20 = 1/So + 1/2So
1/20 = 3/2So
2So = 60
so=30