Answering this simple series question? i don't know what i did wrong!

Looks like you just evaluated the summand for the given value of , whereas the question is asking you to find the value of the sum for the first terms.

Let . Then is the th partial sum.

happens to be the first term in the series, which is why that box is marked correct:



But the next partial sum is not correct:



and this is not the same notion as the second term (which indeed is 0.75) in the series.