What does the ABC stand for in standard form Ax+By=C?

##Ax+By+C## is a generalized form (in fact the standard generalized form) for a linear equation where ##A, B, and C## are placeholders for constants (the ##x## and ##y## are variables).

The generalized form, ##Ax+By+C##, includes equations such as ##color(white)("XXXXX")####7x+3y=98## ##color(white)("XXXXX")####(1)x+(-5)y=14## ##color(white)("XXXXX")####9261x+83y=-7491## ##color(white)("XXXXX")####color(white)("XXXXX")##any infinitely many others

By normal usage ##A## should be an integer value which is not negative.