My_first_geogebra_success

This is my successful attempt to get something useful out of Geogebra. It is a modest beginning; but something tells me I have just unlocked the door on a treasure trove.
I have a couple of questions: 1. how do I lock the point A at say, (1,1)? 2. when I zoom in on that point, I lose my grid: how to set grid so that it stays the same, relative to the current view? 3. this is a simple, modest piece of work: are there any obvious things I could to improve on it, given it's modest aims