deret geometri U4:U6=P U2xU8=1/P tentukan suku pertama?

P = U4/U6
P = ar^3/ar^5
P = 1/r²

U2 x U8 = 1/p
(ar)(ar^7) = 1/1/r²
a².r^8 = r²
a² = r²/r^8
a = √1/r^6
a = 1/r³