mhon bantuanya teman teman...

n=5
r=4
S5=1023
deret geometri naik jika r>1
Sn=a(r^n - 1)/r-1
1023=a(4^5 - 1)/4-1
1023x3=1023a
a=1023x3/1023
a=3
Un=ar^n-1
U4=3.4^4-1
=3.4^3
=3.64=192