Given a quadratic function, y = a x squared + b x + c, what happens to the graph when "a" is positive? a. the parabola opens down, the vertex is the maximum value c. the parabola opens up, the vertex is the maximum value b. the parabola opens down, the vertex is the minimum value d. the parabola opens up, the vertex is the minimum value Please select the best answer from the choices provided A B C D
