Vertex of a Function
The vertex of a quadratic function can be looked at in two different ways. The vertex is where the graph of a quadratic function changes direction. It is also the lowest or highest point on a graph.
Analyze the graph below.
Graph of Vertex and Axis of Symmetry
Notice that on this graph the vertex is the highest point. It is also the point at which the graph changes direction. The line that cuts the graph in half is called the
axis of symmetry. If we were to flip this graph around so that it pointed upwards, the vertex would then be the lowest point on the graph.
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