Question

Jika barisan geometri n-3, n, 3n-6....
tentukan Rasio, Rumus Un, U15
tolong dong

Answer 1

Diket.: barisan geometri n-3, n, 3n-6,....
Ditanyakan: rasio, Un, U15?
Jawab:
(a)Rasio (r) = U2/U1, atau Un/Un-1 = (3n-6)/n = n/(n-3), maka:
(3n-6)(n-3) = n^2, 2n^2-15n+18 = 0, (2n-3)(n-6) = 0, n=6, dan n=3/2,
r=n/(n-3) = 6/(6-3) = 2
(b) Un = ar^n-1, a=n-3, r=2 maka:
Un = (n-3)(2)^n-1
(c) U15 = (15-3)(2)^15-1 = (12)(2)^14 = (12)(16.384) = 196.608