Answers

2016-06-28T15:00:26+08:00
First, we need to find the n term
an = a1r^n-1
46 875 = 3(5)^n-1
15 625 = 5 ^n-1
 trial and error
5^6 = 15 625 (it means n should equal to 7)

we can proceed to find the sum
sn=a1 (1-r^n)/1-r
sn=3 (1-5^7)/1-5)
sn=3 (1-78125)/-4
sn=3 (-78124)/-4
sn= -234372/-4
sn= 58593 (final answer)
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