Why is f (x) = (3x + 1/3)^2 + 8/9 not the vertex form of f (x) not the vertex form of f (x) = 9x^2 +2x +1?
O The expression has a constant outside of the squared term.
O Some of the terms are fractions instead of integers.
O The expression is not the product of two binomials.
O The variable x has a coefficient.