Deret geometri U1= 1 U4=27 Berapa S6= ka tolong bantuin menjawab pake cara ya

U1=a=1

Un=ar^(n-1)
U4=1×r^3
27=r^3
r=3

Sn=a(r^n -1)/r-1
S6=1(3^6 -1)/3-1
=1(729-1)/2
=728/2
=364