Well you can do it in a few different ways.
If you represent your system as <x2,y,z> then your co-ordinate system will look like a normal Cartesian system with the negative region for x < 0 removed entirely.
However if you want to represent <x,y,z>, then you will get a contracted transformed version of the x-axis, but if you are going from the x2 to x, then you have the branch problem since you lose information of the sign by squaring the term.
What happens is that for x as opposed to its square, the rate of change along the axis is not uniform or linear, but non-linear: in the linear case if you double the magnitude on the x-axis you double the x value but in a non-linear if you double the magnitude the value is not simple double: it is less or greater than.