Answer: The sum of the first 8 terms is 765
Explanation:
For a geometric series, the common ratio (r) must equal T₃/T₂ = T₂/T₁
Therefore, 12/6 = 6/3
r=2
Now we know the ratio is 2 we can use the Sn formula to find the first eight terms.
Sn = a(rⁿ - 1) / r-1
a(first term) = 3, r= 2, n=8
S₈ = 3(2⁸ -1) / 2-1
= 765