Jawabanmu

2014-03-15T21:05:18+07:00
Cermin cekung
M = h`/h
      = 4.h/h
       = 4
M = s`/s
4 = s` /100
    s` = 400
/s + I/s` = I/f
I/100 + I/400 = I/f
 5/400 = I/f 
    f = 80 cm