math college

Question

Find the sum of the first 12 terms of the geometric sequence: 2, 6, 18, 54,….

Answer 1

S=a(r^n-1)/(r-1) where a=first term, r=common ratio, n=# of terms

S=2(3^12-1)/(3-1)

S=2(531,441-1)/2

S=531,440   (the 2's cancel)