Jawabanmu

2014-06-11T21:45:35+07:00
128 = r.r.t
Lp = 2 . 3,14 . r (r+t)
agar Lp kecil t = 8 (C)
Jawaban paling cerdas!
2014-06-11T22:04:04+07:00
V = pi.r^2.t = 128pi
t= 128/r^2..........(1)

L = 2pi r^2 + 2pirt
L = 2pi r^2 + 2pi r x 128/r^2
L = 2pi r^2 + 2pi x 128/r
L = 2pi r^2 + 256pi r^-1
L = 4pi r - 256pi r^-2 = 0
4pi r = 256pi / r^2
r^3 =  64
r = 4

t= 128/r^2 = 128 / (4)^2 = 128/16 = 8 (c)
1 5 1