Question 1046326
sum is the sum of a1(1-r^(n+1))/(1-r)
3 is the common ratio, the first term is 1
The last term is 3^6, the first term is 3^0, so we use 3^(n+1) in the formula
1(1-3^7)/(-2)
-2186*(-1/2)=1093
check:
1+3+9+27+81+243+729=1093