Answer:(first term)
a=27(4th term)
T4= a x r^3 = 64
substituting a as 27 in T4
27 x r^3 = 64
r^3 = 64/27
r=4/3
so; a=27, r=4/3
using the general formula of geometric progression,
a x r^n-1
substitute:.
27 x 4/3^n-1
= 27(4/3)^n-1
Answer: (C) HOPE THIS HELPS!
