diketahui barisan geometri 3,-6,12,-24,...,768 tentukan n ?

3,-6,12,-24,...,768
Un = a.r^(n-1)
768 = 3.(-2)^(n-1)
768/3 = (-2)^(n-1)
256 = (-2)^(n-1)
2^8 = (-2)^(n-1)
(-2)^8 = (-2)^(n-1)
8 = n-1
8+1=n
n = 9

n = 9
3, -6, 12, -24, 48, -96, 192, -384, 768