does not look like a polynomial equation because it does not closely resemble the
standard form of a polynomial equation given above.
However, if you FOIL this formula and carefully simplify then you can get the equation
to resemble the standard form, and confirm that it is, indeed, a polynomial
equation.
Doing this:
y = (x +1) · (x - 4) · (x - 4)
(FOIL (x - 1) and (x - 4))
y = (x2 - 3 · x - 4) · (x - 4)
(FOIL again)
y = x · (x2 - 3 · x - 4) - 4 · (x2 - 3
· x - 4)
(Multiply through)
y = x3 - 3 · x2 - 4 · x - 4 · x2 +12
· x +16
(Collect like terms)
y = x3 - 7 · x2 + 8 · x +16
(Collect like terms)
This looks exactly like the standard form of the formula for a polynomial
equation. So,
although the equation did not initially look very much like a polynomial
equation, it
turned out to be a polynomial because it was possible to expand and simplify the
equation, eventually making it resemble the standard form for a polynomial
equation.