Jawabanmu

2014-06-10T06:20:18+07:00
-1/si + 1/so = -1/f
-1/60 + 1/30 = 1/60
f= -60 cm
2014-06-10T06:49:52+07:00
Dik : s=30cm
m=2x
dit: R=.....?
jwb: m=so\si
si= 30cm:2=15cm
sudah dapat sekarang kita cari f
1/f=1/so+1/si
1/f=1/30cm+1/15cm
1/f=1/30cm+2/30cm
1/f=3/30cm
f=10cm

R= 2xf=2×10cm=20cm
maka jari2 kelengkungan cermin(R) =20 cm