Two ways outlined here are basically the same, just that the one below, the addition component has an expression to modify Inputs A and B: Abs(A) and Abs(B) respectively.
Hi Ryles, hi Luis,
is it possible that this method does not work if the domain is from -10 to -10?
Here a small modification that uses Grasshopper's internal logic. The function is only necessary if the outputs need to be always positive. Or did you need to always sum the absolute values in every case?