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.