So, i'm to understand that "0 - -a = a" and I can understand this, in the context of say, being at an arbitrary reference point called "0" and then on a 2 dimension Cartesian graph of + shape and the operator "-", which can mean to reverse (so turn around 180 degrees) and then the second minus symbol to turn around 180 degrees from here (so to turn full circle in this instance) and thus move forward [positive] "a". However, if the "-a" is to represent debt, which can be represented by negative number, then with, of course, the operator "-" meaning to take away then "0 - -a" can be read as: nothing '' to take away '' '' to take away ''a'' '' and so, given the debt (that is, ''-a'') is to be taken away, then there would just be 0, that is, 0 - -a= 0 and not the 0 - -a=a as with coordinate geometry in mathematics. I'm wondering whether there is information out there on said differences which appear between coordinate geometry and non-coordinate geometry? Second part of the question, as it is sort of related to the first question, is that of the imaginary number "i", which as i'm to understand is "square-root of -1". Whereby, if one does have a square with unit 1 but the direction is either in the conventional downwards, leftwards or backwards direction, then surely the "square-root" function just refers to one side of the square because after all, say, a square with an area of 4, would have a square-root of 2 as this is the length of one of the sides of the perimeter of the square with an area of 4 and of course, the length of one of the sides of a square with an area of 1 is 1 unit. But surely this depends on the side of the square that is taken? Is there any convention to determine which side of the square the square-root pertains to? Because a square with an area 1, which is said to be negative might only refer to a one direction that is negative (so a square that is in the top-left or bottom-right quadrant, by convention), in which case the "square-root of -1" (or "i") could be either -1 or +1 and not just merely a so-called imaginary number. Or am I really way-off with this? If so, please explain in lay terms as to why I am because, of course, I have deliberated over this matter considerably and sense some truth in what i'm describing. Many thanks for your patience with a non-graduate in Mathematics (though a graduate).