What is the sum of the first 6 terms of this geometric sequence? 1, 8, 64, 512, …

Use the formula. Sn=a1(1−r^n) / 1−r, Where a1 is the first term (1 in this case), r is 8, and n is the number of terms. So  1(1-8^6) / 1-8

The first one, i believe, would be correct. all the others have one thing in common, and that's that they have repeating numbers. in the second one, x and y have repeating 6's and 3's, and in the third, x and y have repeating 6's as well. in the last one, there are repeating 3's. the first one has no repeating numbers.

The answer is 60.9774