Technique used to solve certain types of differential equations. This technique involves collecting all of the variables in the equation with their corresponding d. Rei:

x dy + y dx=0

x dy=-y dx                    <- organizing equation

dy/y = -dx/x                  <- dividing by x and y - separating equation

Sdy/y=-Sdx/x                  <- integrate both sides

ln|y| + c1 = -ln|x| + c2      <- fundamental theorem of Calculus

ln|y|+ln|x| = C               <- collecting constants

e^(ln|y*x|)= e^C              <- simplifying

y*x=C2                        <- simplifying further - new constant