Early Styles (Musicians Active before 1930)
Early Country Blues
Early Urban Blues
Early Jazz Blues
Kansas City Blues
Later Styles
Post War Jazz Blues
Chicago Blues
Modern Blues (post 1950s)
Blues in conventional pop music
... is to add a constant (i.e., in this case, a quantity that does not depend on x) to the expression to the left of "=", that will make it a perfect square trinomial of the ...