diketahui barisan geometri U3=2 U7=32 U9=?

Un=ar^n-1
U3=ar^2=2
U7=ar^6=32
a=2/r^2 (1)
a=32/r^6 (2)
a(1)=a(2) = 2/r^2 = 32/r^6 = r^6/r^2 = 32/2
= r^6-2 = 16 > r^4 = 16 MAKA r = 2(akar4 dari 16)
a=2/2^2= 2/4 = 1/2 / a=32/r^6 = 32/64 = 1/2
U9=1/2r^8 = 1/2 x 256 = 128