Jawabanmu

2014-03-02T13:22:15+07:00
S tak hingga = a/(1-r)
72=a/(1-r)

jumlah semua suku ganjil -> r'=r²
Sg=a/(1-r²)
48=a/(1-r²)

 \frac{72}{48} = \frac{ \frac{a}{(1-r)}}{ \frac{a}{(1- r^{2}) }}
 \frac{3}{2} = \frac{1-r^2}{1-r}
 \frac{3}{2} =  \frac{(1-r) (1+r)}{1-r}
 \frac{3}{2} = 1+r
2+2r=3
r=1/2

72=a/(1-1/2)
72=a/(1/2)
a=36

Un=a*r^(n-1)
U3=36*(1/2)^2=9
2 3 2
2014-03-02T16:10:51+07:00
S tak hingga = a/(1-r)
72=a/(1-r)

jumlah semua suku ganjil -> r'=r²
Sg=a/(1-r²)
48=a/(1-r²)





2+2r=3
r=1/2

72=a/(1-1/2)
72=a/(1/2)
a=36

Un=a*r^(n-1)
U3=36*(1/2)^2=9


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