Question

No. 24 tlg bntu ya + crany!

Answer 1

U2=ar =30
U5=ar^4=240
= ar . r^3=240
= 30 . r^3=240
r^3= 240/30 = 8
r = 2
ar=30
a.2 = 30
a= 30/2= 15
S7=a(r^7 -1)/(r-1)
= 15 (2^7 -1)/2-1
= 15 (128 - 1)
= 15 . 127 = 1905