The Quadratic Formula uses the "a", "b", and
"c" from "ax^{2} + bx + c", where "a", "b", and "c" are just
numbers; they are the "numerical coefficients" of the quadratic
equation they've given you to solve.

Forms with a=0, that yield ax^{2} + bx + c = bx + c only,
are not considered quadratic, but rather linear.