> 1+3¹+3²+3³+3^n = (3^(n-1)-1)/(n-1) Sorry to be pedantic, but this contains 3 [sic] errors. 1) it's missing a ... denoting n-4 terms between 3³ and 3^n 2) t

> 1+3¹+3²+3³+3^n = (3^(n-1)-1)/(n-1) Sorry to be pedantic, but this contains 3 [sic] errors. 1) it's missing a ... denoting n-4 terms between 3³ and 3^n 2) the exponent on the right should be n+1 instead of n-1 3) the denominator on the right should be 3-1 instead of n-1