1. Linear, constant, and squaring functions are examples of ________ functions.
2. A polynomial function of x with degree n has the form f (x) = anxn + an−1xn 1 + . . . + a1x + a0
(an ≠ 0), where n is a ________ ________ and an, an−1, . . . , a1, a0 are ________ numbers.
3. A ________ function is a second-degree polynomial function, and its graph is called a ________.
4. When the graph of a quadratic function opens downward, its leading coefficient is ________ and the vertex of the graph is a ________.