Gauss Algorithm for Square Root of 2

I did this all in Chrome.

First with Google Docs I made a spreadsheet with the formulae:

1/x -[1/x]

0< x <1

  x = 2^1/2 - 1

I generated thirty values using the previous row to calculate the present row.

I plotted in each row (x + 1)².

Initially rounding errors give 2, then it deteriorates as you can see.