The graph of a quadratic function has a domain of (-∞, ∞) and range of [4, ∞). In two or more complete sentences, explain how the given range of the function can help you to determine whether the graph opens up or down.
The range of the function indicates that the function has a vertex at y=4. The number on the left in the range notation is the lowest point, the number on the right is the highest point. Since the number on the right is ∞, the graph must open up and have a minimum at 4.
