By the dot product n. If all variables represent real numbers one can graph the equation by plotting enough points to recognize a pattern and then connect the points to include all points. In case the given equation is in polar form then search for r²or rcos Ɵor rsin Ɵ but in case of Cartesian equation then look for x²y² or x or y.
The advantage of this is that you may insert the values of the other variables if you know them then you just have to do a simple calculation.
P AxByCz which is the result you have observed for the left hand side. In case you have squares in the equation try to complete it. Once you have found the required elements start substituting. Shortest distance between two lines.