Question

The parabola representing a quadratic polynomial f(x) = ax² + bx + c opens downward when ______.

Answer 1

The parabola representing a quadratic polynomial f(x) = ax² + bx + c opens downward when a < 0.

Explanation:

The sign of the leading coefficient a determines the concavity; if a is negative then f''(x) = 2a < 0, so the graph is concave down and the vertex is a maximum.