Work on your prompts. Break down the problem into pseudocode steps, the way you might write down comments for yourself on how to do something. Provide examples of similar working code if you can. Don't ask it to do everything at the same time, break it up into limited goal increments.

In my experience LLMs work best if you already know how to do something, but you just can't be bothered to actually do it.

When exploring unknown territory, keep your questions simple and ask for clarification on anything you don't understand. It will not just help you, but the AI as well.

> I wanted some way of calculating the sum of a geometric series without having the series in actual cells.

There are simple explicit formulas for this.

yeah, sumproduct on google docs was the thing it kept suggesting, but not in a way that worked for the thing I wanted. I found a way around it in the end, but I feel I wasted 30 mins trying to get ChatGPT to understand what I wanted and give me something that actually worked.

\sum_{i=0}^n x^i (the sum of all terms x^i as i ranges from 0 to n, inclusive) = (x^{n+1} - 1)/(x-1).

Or, if n is positive infinity, you assume that |x| < 1 and thus the sum is (0 - 1) / (x-1) = 1/(1-x).

If you need the sum from x^m to x^n, that's equal to the sum from 0 to n minus the sum from 0 to (m-1).

You can derive the formula yourself without difficulty:

         sum = 1 + x + x^2 + ... + x^n
    (sum)(x) =     x + x^2 + ... + x^n + x^{n+1}

    (sum)(x) - sum =  x^{n+1} - 1
    (sum)(x-1)     =  x^{n+1} - 1
    (sum)          = (x^{n+1} - 1)/(x-1)