Hello,
Let the Series be:
a, ar, ar^2 ... so the sum will be:
a/1-r=14......(1)
now we cubed the series so terms become:
a^3, (ar)^3, (ar^2)^3... So the sum of this series will be
a^3/1-r^3=392......(2)
Solve (1) and (2) to get the answer.
Hope this Helps,
All the Best.
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