sat-dog

Choice A is correct. The given quadratic function f is in vertex form, , where is the vertex of the graph of in the xy-plane. Therefore, the vertex of the graph of is . In addition, the y-coordinate of the vertex represents either the minimum or maximum value of a quadratic function, depending on whether the graph of the function opens upward or downward. Since the leading coefficient of f (the coefficient of the term ) is 1, which is positive, the graph of opens upward. It follows that at , the minimum value of the function f is .

Choice B is incorrect and may result from making a sign error and from using the x-coordinate of the vertex. Choice C is incorrect and may result from using the x-coordinate of the vertex. Choice D is incorrect and may result from making a sign error.