Example Find the vertex for the graph of Support your answer graphically. Solution a = 2 and b = 8 Substitute into the equation to find the y-value. The vertex is ( 2, 11), which is supported by the graph.
Example Compare the graph of g(x) = –4x 2 to the graph of f(x) = x 2. Then graph both functions on the same coordinate axes. Solution Both graphs are parabolas. The graph of g opens downward and is narrower than the graph of f.